Although this could be a factor, I have to disagree on this. Before any foreign student is given admission to an American University you need to take TOEFL (Test of English as a Foreign Language). You need this to be a high score to get admitted and depending on the country, you need to show this score at the American Embassy to get a student Visa. Unless it is some exchange program ALL foreign university students can speak English on a conversational level.

I am from Nigeria, where English is the National language. I grew up visiting America as a child because my parents grew up there for some portion of their lives. So even with all my linguistic advantages I still bonded more with other International students faster and better than I did with Americans (regardless of race).

I would say the issue I found was cultural, basic things like sense of humor differs. What a Nigerian finds funny is not always the same thing an American would find funny and vice versa.If you cannot laugh together, you have a problem. Same with etiquette, some things a Nigerian may do might be seen as rude to an American but a sign of love in Nigeria. The second issue I found is that Americans don't have a lot of curiosity beyond their own culture. A lot of Americans have the idea America is the best country in the world, so what could they learn from anyone else when they push the world forward, so there is a lack of interest to understand others perspectives and there is a gap.

I personally worked hard to have American friends and I have life long ones today both white,black, latino and Asian American friends but this did not come easy. This took about 10 years of open-mindedness and extroversion that was not always reciprocated.