When I was studying abroad I was asked all the time what it was like to live in The States, and I always had to explain how different each state was from even its neighboring states. So I pretty much told everyone that what they were really asking was "whats is it like to live in your region," and that I didn't know what it was like to live in California or Texas (I image that its noticeably different). Its really interesting vising a country where everyone is so similar no matter what city you visit. It would be wired not having that city/state rivalry I'm used to.
I know what you mean. Though everywhere has their regional cultures and rivalries, I think that it's hard to grasp, even for Americans, just how vast the country is. A friend from England once asked me if I knew all the counties in the U.S., which was a reasonable question from his perspective as a lot of people in England are familiar with the English counties and their distinct accents and customs. I don't even know all the counties in my state and I live in a pretty small one.