C-
It's all in the name/Decent amount of tolerance
While there are students from all over the country and from MOST parts of the world (Most foreign kids are either Chinese, Indian or European), the vast majority of students at NU are white, suburban, mostly upper-middle to upper class kids from the Northeast. There seems to be a general tolerance towards diversity, but there have been occasions where students just lost their cool against kids from other backgrounds.
(Quick point about foreigners: Even though there are foreigners, most of them have actually lived in the USA before coming to college. I only know like 3-4 foreigners that have been born abroad AND never lived in the US before college.)