If I were trying to model what it takes to become a world power in a competitive strategy game these would be the key factors I'd use:

• A single contiguous common market (currency, language, culture)
• A large population
• Abundant natural resources
• A free press
• Sufficient access to the ocean
• Relatively low tax rates (limited government)
• Relatively few impediments to starting a business
• Strong property rights laws (both physical and intellectual property)
• Light regulation on businesses
• A reasonably educated population
• An egalitarian culture

A nation would need most if not all these things to be a major world power economically. Most of these are matters of degree (how "free" does the press need to be for instance). As a model, I would put a weighting factor next to each and then rate each category. Then it would be a matter of multiplying the weighting and rating and then summing up the total.

Americans, for example, tend to believe that they live in the most powerful country in the world due to their inherent American spirit of liberty and equal opportunity. But that's really not the whole story.  The United States benefits from these factors in ways that most countries simply cannot. Let's look at these with a bit more detail.

First off, the United States has a continent spanning contiguous market that is roughly the size of Europe. But unlike Europe, which has dozens of native languages actively spoken, English is predominantly spoken as the native language regardless of whether you're in California or Indiana.  This is key as it lowers barriers to entry for products and streamlines the introduction of services.

Secondly, the United States has a population of around 300 million people. That's a lot of people you can sell to without having to go through much effort.

Thirdly, the US has massive amounts of natural resources. It's not commonly known but the United States is the world's largest producer of oil.  Not Saudi Arabia, not Kuwait. It's just the US uses so much oil it still has to import. But that should give you an idea of the kinds of natural resources the US has going for it across the board -- because it's also the world's largest producer of food. The two basic things for a modern society -- food and energy, the US has a lot of it.

Fourth, a free press is important because it helps ferret out corruption and act as a information channel for new products and services based, largely, on merit.

Fifth, the United States has the world's largest coastline. The movement of goods, particularly industrial and food, are still done largely by ship. Bulk goods are too expensive to be flown from destination to destination. You need waterways to import and export cheaply and the US is geographically located with an ocean that connects it to Asia and another one that connects it to Europe and Africa. 

Sixth, the US has relatively low tax rates. This is important because it creates an incentive for people to start their own businesses. Wealth is a powerful motivator. It also has the side effect of keeping the government (relatively) small as a share of the GDP which keeps it from mucking things up too much.

Seventh, it is very easy to start a business in the United States. Just fill out a few forms and you're set. In India, for example, it's a nightmare to get a business going. China isn't much better.

Eighth, property rights are key. The US has lots of courts and lawyers (arguably too many). The system is set up to make it easy to enforce your property rights. Some would say (including me) it's a bit too easy to sue people in the United States but it does have the advantage of discouraging people from pilfering other people's stuff in business or selling shoddy products.

Ninth, you can run your own business without being bogged down (too much) by regulation. This can have some nasty side effects (environmental, workers rights, etc.) but it does make it easier to have a business and if a strong economy is your goal (which it isn't necessarily everyone's goal) then less regulation is better.

Tenth, your population has to be well educated. I realize according to "tests" the average American is about as smart as a toad stool. But the question isn't who is smarter or better educated, the question is whether they are educated enough. So far, the answer is that whatever invisible threshold of adequacy exists, Americans still squeak past it.

And lastly, an egalitarian culture. Americans are by no means perfect here. There is still widespread discrimination between different races. But compared to other countries, the US is pretty egalitarian. Racism in the US requires a change in pigment (i.e. black, white, brown, etc.). In other countries, Japan, Korea, India, many parts of Europe, racism is between people of the same race (from our vantage point) because of family or geographical ties. In India, what caste you came from matters. It even matters in Japan. But that's nothing compared to what the middle east has going against it -- they discriminate against half their population -- women.  You throw out the potential contribution of half your population and you can't possibly compete against those who are using most or virtually all their potential.

On none of these issues is the United States perfect. A lot of this comes down to being in the right place at the right time. These factors weren't really imagined prior to the industrial revolution. And going into the future there are other nations who have the potential to exceed the United States.

For example, China has the potential to meet and exceed these items to become the world's most powerful nation. It has a lot of things it has to fix up first but they are on the right track. China isn't yet a single market in the sense we're talking. It has many regional cultures and languages that impede business. They also have to work on their internal infrastructure, educational system, and red tape problems. But these are all things that can be addressed.

By contrast, Japan is not going to be able to get much stronger than it already is. It's already about as good as it's going to get. It could be a bit more egalitarian but one could envision a future where Indonesia has caught up or surpassed Japan a hundred years from now.

India is another potential case. But it has multiple very distinct languages. You've got Hindi and Punjabi and dozens of others. But again, down the line, they could standardize on Hindi as the primary language (or English) and take care of that. But they also have massive massive problems with red tape there. The amount of regulation going on there to start a businesses is unreal. They also have serious egalitarian problems with the leftovers of the caste system. These cultural issues will take a long time to take care of so I don't really expect India to be a huge economic power in my lifetime but I could be wrong.

The European Union is not in very good shape on most of these issues. As individual units, Germany, France, UK, Belgium, Netherlands, Sweden, Norway, Finland, Poland, etc. are all pretty decent on these issues. Give any of them 300 million people, more natural resources, and voila, you have insta-super power. But the EU will not be greater than the sum of its parts -- not in the foreseeable future. It has massive language issues. It has excessive taxation in some parts. It has problems with scaling -- you'll hear someone say "Well, Finland is doing this and that..." And Finland has a population of 5 million people that are all virtually identical culturally (99% white). We have cities with larger populations than Finland. A lot of government programs don't scale too well when you get into larger populations over a wide geographic scale encompassing different cultures.

The biggest problem the EU faces is population decline. So even if it can manage to get the different components to like each other (i.e. not discriminate against each other in hiring) and understand each other linguistically and lower taxes, they still have the problem of actually losing population. They have to reverse that trend to even have a hope to deal with the other issues. I have friends in Europe and like I said, as individual countries do they do fine. But the EU won't scale so well.  In the United States, no one looks at someone's job application and thinks "Hmm, they're from Idaho, those bastards!" But I've seen how different people in Europe react to people from other parts of Europe, which part of Europe you come from matters and will continue to matter for the foreseable future.

Brazil is another potential but it isn't likely to supplant the United States. It has many of the same natural things going for it as the US does but not as much so. But I would expect Brazil to become a bigger player in the future.

As for Africa, the whole continent seems a lost cause. I can't think of a single nation in Africa with the potential to become a major player this century.

Meanwhile, Canada has a lot going for it but lacks the population. Its total population is less than California. It also has increasing polarization. There's a real possibility that 100 years hence we could see Canada break into 3 nations -- Quebec, Ontario, and the western provinces. The cultural differences between the 3 are quite stark.  The major issue is population and high taxes.  But because Canadians have a huge border with the United States, huge coastlines, great natural resources, and lower labor costs, it benefits a great deal from its location and if it can get is population growing faster, it will become an increasing factor. That said, it'll be a long time before it has any chance of being a global super power.

So that leaves Russia, one country that I think has an excellent chance of becoming a true economic super power. First, they have an educated work force. Secondly, they have incredible natural resources. Third, they are in an even better geographic position than the United States is for world trade -- it doesn't need ships to transport to Asia and Europe, it's already there!  So what's Russia's problem?  Russia has a massively corrupt domestic government, a corrupt judicial system, poor enforcement of property rights, a culture that has very little respect for property still (thank you communism), and an infrastructure that's decayed.  If it can solve these things, it's in great shape. It's relatively egalitarian -- more so in many ways than the United States. It has a cheap work force that is well educated and lots of people to sell stuff to locally. If they can just fix their government to be less corrupt they have an excellent shot.

So there you have it. When someone says that the United States is doomed to "decline" they need to look at what factors they think it will falter at and see if those things are likely to bring about this decline. Decline can come in two forms: Real decline and relative decline.  I can envision both scenarios for the United States.  The slow increase in regulation and taxation in the United States is slowing down business growth in key sectors (outsourcing has become a major issue -- start looking at how much stuff you use is now made in China).  The educational system is increasingly soft relative to its competitors which could make its workforce less competitive. 

But realistically, while I can envision decline scenarios, I don't see a scenario where the US ends up anything other than sharing the world economic superpower neighborhood with maybe China and Russia a hundred years hence and that's a big if. Those who dislike the United States and speak of its imminent decline seem to imagine such decline purely because they wish it very very much. Economic decline isn't magic. Wealth and success on the macro scale isn't based on karma and good will. Concepts like "Decadence" only become an issue if decadence is translated into governmental policy (such as massive entitlement programs for those who don't want to work as we've seen in France). Decline is based on very specific factors that are generally understood by economists. 

No one can predict with certainty where we'll be in 100 years hence or whether the United States or China or some other country will be the most powerful nation in the world. But I think we can reasonably project where they'll be -- for whatever it's worth.