Is there any real American food?

Except McDonalds, or are they all imported from other countries?

Cornbread was originally an Amerind food.  The aboriginal inhabitants of North America cultivated a number of vegetables and grains unknown in the rest of the world, including tomatoes, potatoes, hot peppers, maize, string beans, and many species of squash.

Chop suey was created in San Francisco by Chinese immigrants using Chinese cooking techniques and the vegetables and other ingredients locally available.  It is only faintly similar to the Cantonese dish, lo mein.

Any dish made anywhere in the world using tomatoes, potatoes, hot peppers, pumpkin, string beans, or maize is using vegetables first cultivated in the Americas.  In a very real sense, kimchi, polenta, potato latkes, mealie-pap (African cornmeal porridge) and ravioli are foods with roots in the New World.

Are there foods distinctly USAian, that the rest of the world doesn't eat?  Sure.  Pumpkin pie.  Spam.  Roast turkey.  Hamburgers and weenies were German creations that the Germans, perhaps wisely, decided to abandon before the turn of the century, but Americans adopted them quite enthusiastically.  Chicago style pizza looks about as much like Sicilian pizza as chop suey looks like lo mein.  Macaroni and cheese--no, wait, the Canadians eat that too.  New England boiled dinner.  New York Jewish delicatessen style kosher dill pickles don't exist anywhere else on Earth today, though maybe 75 years ago you could have gotten them in Warsaw or Berlin.  American delicatessen style corned beef is likewise unique today, though Irishmen 150 years ago might have recognized it.