Obviously there are some people who are racist against other groups of people, so they won't want to associate with anyone else outside of their own race/ethnic group.

However, I think most people don't try to separate themselves by racial groups, but they tend to do so anyway. You're usually friends with people who live near you/interact with you reguarly, and in a lot of cases, you live in places where there are other people of your race. 

People also like to be friends with those they have more in common with. My high school was really diverse, but there was still a tendency for white kids to hang out with other white kids, Latino kids with other Latino kids, Asian kids with other Asian kids. Everyone got along fine with people of other races, but when it came to choosing friends, people were more comfortable being around those of their own racial group.

I also agree with Dave about socio-economic status. Your status often affects where you live, where you work, where you go to school, etc. And, due to a few social factors, some races are statiscally better off financially than others, so this also adds to the equation.

I will break it down for you:

People in America tend to only interact with people of their own "financial group" . Race has little to do with dictating social interaction only money does usually.

I must admit that some clannish folk do tend to stick to only each other (ultra-conservative religious types usually), but they are usually new to usa and not americanized yet so to speak.

I was kicked out of a Chinese apartment complex over 20 years ago because they found out I was white haha. Usually the people that seperate themselves have strong beliefs (religious or moral) and they do not want to lose any of that with some American materialist hedonistic values.

You have racist people in this country that would only stick with their which is sad. Most Americans, such as myself, don't care about race when talking or getting to know people.

You have racist people in this country that would only stick with their kind which is sad. Most Americans, such as myself, don't care about race when talking or getting to know people.

yes and no