If you want real US food you'd have to do a litte digging ... Louisana is probably the easiest with their creole/cajun food, then there's Southwest cooking (not Mexican - it has it's own flavor). Here in the Pacific Northwest you can get regional American Indian cooking.Most major cities have 'authentic' ethnic restaurants, but they're also not easy to find. People here tend to like 'comfort food' - the things they grew up eating. The chinese restaurant I go to here serves a lot of dishes that aren't even on the menu - I think they'd scare most people away! When I go in I always have to ask the server, 'What is that table over there eating?'
The US isn't called the melting pot for nothing ... most of our food is like our population, a mixture of old and new, and generally pretty tame. If you like steak & potatoes this is the country for you! If you prefer fish innards or sweetbreads you'll be going hungry most of the time