We tend to divide up over regions (North/South; East/West' Midwest/everyone else); by state (too many to name); by city (San Francisco vs LA; New York vs Chicago; etc).
People say America exists because it's a 'melting pot' - sometimes, I think it exists because it's so big that people in different places can pretend they are autonomous . . .
I dislike 'othering' but it's human nature to define oneself against someone else - much easier to say 'we are NOT like THEM' than to say 'we are essentially the same' . . .