Hawaii: Anything Asian (look in little Mom & Pop places in strip malls where no one uses a fork), anything fresh ocean fish. Saimin (or any noodle shop), Poke, Lomilomi, huli huli chicken or pork, kalua pork, chicken long rice. Portuguese bean soup, Big Island beef. Anything with Portuguese sausage. Chili Rice.
Florida: Rock shrimp, anything Cuban
Illinois: Italian roast beef sandwich and of course Chicago Pizza
Anywhere in the southwest: Anything Mexican. It will vary some from state to state, as with most of the U.S., everyone has their own twist. Look for little places in strip malls where no one speaks English
New England: Boiled dinners, shellfish of all sorts
Virginia: Hams, but also most smoked meats and anything pork
Iowa: Anything pork, especially tenderloin sandwiches
California: Santa Barbara Barbecue (grilled tri-tips with pinquinto beans)