America also has a cultural obsession with self-reliance/liberty/frontier-as-a-virtue which makes "socializing" a bit of a taboo concept, in a weird way. It's a crutch to "need" to be around others, despite it being fundamentally human to feel this way.
When you combine these two things, I think you get a group of people who need to interact with one another, but also kind of hate one another, and refuse to admit the dichotomy. What we've discovered then, is by heavy drinking we can start to pick at those barriers, though maybe that is, itself, part of the problem.
[0] https://en.wikipedia.org/wiki/List_of_countries_ranked_by_ethnic_and_cultural_diversity_level