IME, that's imagined as much as anything. I'm not going to say that it doesn't exist, but it's mostly propaganda used by people in non-urban areas to build their own followings and consolidate their own power. In reality, it doesn't comport with the way people on the coasts actually think - beyond being frustrated at some of your political ideas, most of us just don't really care one way or another. But the real fallacy baked into that message is that we on the coasts don't know anybody from these non-urban, non-coastal areas and that your culture is entirely foreign to us. It just isn't true. Yeah, some of us grew up in big cities, but a lot of us are transplants who moved here for work. For example, just in my church community group (in Baltimore City), there's me and another guy who both grew up in the rust belt region of central/western NY, a post-doc from a farm in eastern Washington, a grad student and his wife from middle-of-nowhere Kentucky, an undergrad from a huge farm in Oklahoma, a grad student and her husband from Montana, and a social worker from South Carolina. At my last church in the middle of Cambridge, MA, there were so many people from Oklahoma it became sort of a running joke.
That's got nothing to do with culture and everything to do with money. Those groups both pay the full sticker price and don't dip into the school's financial aid pool.
No, I don't personally feel like that - mainly because identities of that sort don't really appeal to me - but I also don't discount what you're saying. Part of the issue is that the celebration of "American" culture carries with it a lot of baggage - throughout history, that celebration and that identity has very often been defined by who it excludes rather than just who it includes, so today, even the most well-meaning, non-racist person is going to draw some raised eyebrows when they start heading down that path. Part of it is also the fact that America is pretty new. Most other cultures have had millenia to develop - often in relative isolation (which is where things really become unique); we've had a couple centuries, none of it in isolation. Arguably, a lot of the most uniquely-American elements of our culture have come from the black community: barbecue, jazz, blues, rap.
That said, for someone feeling as you do, there are some encouraging things coming from, all of places, the restaurant industry. My wife and I are kinda-foodies and there's been a big movement in the last few decades to respect and celebrate the unique cultures and ingredients of the different regions within the US. (so much so that if you're a viewer of chef-oriented cooking shows, as we are, it's gotten a bit heavy-handed) A lot of that unique regional flavor (no pun intended) had been sort of washed out in the 20th century partly because so many people treated the fancy European standard as an ideal and partly because it was cheaper for large chains to homogenize everything. But it's now following a somewhat-similar path to music wherein the appreciation of it as an artform has expanded to treat just about every source of influence as worthwhile.