I'm surprised drinking culture hasn't been mentioned more here. As an American who when to an American university, I had no friends who were non-American. When I reflect on the reason for this, I do remember meeting students from other countries but they had different priorities than myself and my group of friends at the time so we never really clicked. (our priority was to go out and drink as often as possible - 4 days per week usually) For someone coming from a country where alcohol is consumed in moderation from young ages, I can see how this would be an unappealing scene to get into.