I don't find this to be true in my experience. Pretty much any moderately-sized university campus in America is a counterpoint to what you're saying. These communities can be very diverse, and while it's true that you can often find various cliques that split along various demographic lines, members of diverse university communities still live, learn, and work in close proximity.

I think implicit in your comment is the assumption that people with different backgrounds are somehow defacto strangers. But what makes it all work on a university campus, imo, is that everyone has a purpose; there are no scary strangers because everyone's motivations are well-understood, since everyone on campus has a job to do. No one is really a stranger.

It doesn't matter if you are of a different color or gender, or that you come from a place I've never been to, or that you speak a language I've never heard, or that you eat food I've never tasted. My lizard brain doesn't kick in when I interact with you because you are just here to study and learn, or to help in that process.

As an example, I am a professor and I have a new colleague. He is from the other side of the world, he was born a decade before me, he eats food different from mine, he worships a different God than I do. But we get along just fine, and that's because despite all those differences, we still have more in common than not. And even if we didn't, we still have to rely on one another and work as a team to achieve a common goal.