Ahmad Jamal called Jazz American Classical music, and while the origins are a little blurred there are firm roots in New Orleans with Creole people and freed/escaped slaves taking refuge with American Indians. It's certainly a true American art form.
Stand up comedy came from vaudeville theatres of New York City. Even now, the greatest stand-ups of all time are all American, and all used the medium for cutting social commentary. Another American art form.
We can't say the same for food. Burgers and hot dogs are extremely German (or Austrian), pizza is very Italian despite the weird Chicago interpretation being like an entirely different food group. And like multiple pubs in England claiming to be the oldest, too many places in the USA claim to be the home of barbecue. And smoking meat started long before the colonisation and foundation of the new world.
I don't know what I'm talking about.