In a comment to an article about racism, someone from Australia made the absurd claim that Australia is the most multi-cultural country in the world. Not to be outdone, someone from Canada claimed the mantle for Canada. What's next? Someone from Japan making that claim?
Here are some statistics on the racial make up of a few selected countries:
Australia: Caucasian 92%, Asian 7%, aboriginal and other 1%
Canada: Canada has diversity if you count various types of white people as diversity. http://www.statcan.ca/english/census96/feb17/eo1can.htm
United States: It's about 62% white, 14% Hispanic (white can be counted as white if you want), 13% African American, 4% Asian.
Getting into a debate about what is the most multi-cultural country in the world is futile because the definition can be played with until it becomes meaningless.
I tend to view the US as pretty multicultural because it has multiple racial groups (defined as people who physically look significantly different) that represent significant percentages of the population. African Americans, Latinos, Whites (various European ancestory), and Asians all make up significant percentages of the population as well as having high enough populations to reach a critical mass.
4% of Americans being Asian represents arouns 12 million people (to put it in perspective, the entire population of Australia is 19 million). 13% of Americans being black means nearly 40 million people (Canada's population is around 30 million total).
When you have those kinds of raw numbers representing a pretty significant percentage of the population, it means each group has to deal with the other in a very real and practical way.
Australia, for instance, being 92% white, claiming to be multicultural is akin to some all white high school claiming to be multicultural because there are 3 Asians and an African in one of their classes.
Europeans who smugly talk about American racism have no idea what they're talking about. Besides the fact that Europeans only recently tried to wipe out one of their own racial minorities in death camps for apparently not being white enough (I tend to think one of the reasons why there's relatively little anti-semitism in the US is that we jsut don't understand it. When you have neighbors and coworkers whos ancestory is from India and Japan and China or African, it's hard to really notice the differences between some guy whose ancestors are from Poland who happened to choose a slightly different religion).
But given how much under observation Americans are, when you have 300 million with minority groups that would be the majority population in most other countries you are bound to have incidents where one group doesn't like another.
Koreans and African Americans in LA notoriously don't get along. I have no idea why. But it's widely reported. African Americans and Jewish people don't get along in New York for some reason. No idea why. And African Americans and some White southerners don't get along. I do have an idea what caused that at least!
But when you mix around so many different cultures and races so much, you're always going to (statistically) have cases where there is conflict.
In Europe (or apparently Australia) cultural diversity means being a slightly different type of European. But in the US, the threshold is much higher. If you're from Europe you're white. Italian, Pole, English, French, whatever, doesn't matter. And if those Europeans who complain about that when they arrive are bound to be eventually rebuked by the Korean or Mandorian Chinese or other type of Asian who says "Hey, welcome to the club, our cultures have been lumped together for centuries by you Europeans!" 