Really? I was born and grew up in a suburb of Chicago, but have since then lived in Los Angeles, Houston, Atlanta, and a few other places, and have rarely felt that my born-in-Chicagoness was at all an important or a distinguishing factor. There are Americans I don't have a lot in common with, but it doesn't have much to do with where we were born. For example, I don't tend to get along with people who have anti-intellectual views, but you find those (and their opposite) anywhere. I think of myself as "American", but I would be hard-pressed to think of anything particularly "Chicagoan" about me. It'd be something trivial like hot-dog or pizza preference, probably.
As far as geography goes, I see more differences within than between regions. I don't have a lot in common with people who live in very rural areas, for example. But e.g. a coffee shop in Midtown Atlanta doesn't feel that much different from a coffee shop in Brooklyn or Westwood. And the Atlanta suburbs don't feel that different from the Chicago suburbs.
As far as geography goes, I see more differences within than between regions. I don't have a lot in common with people who live in very rural areas, for example. But e.g. a coffee shop in Midtown Atlanta doesn't feel that much different from a coffee shop in Brooklyn or Westwood. And the Atlanta suburbs don't feel that different from the Chicago suburbs.