As American as Mac and Cheese is my go-to, since while there were pasta and cheese sauce dishes elsewhere, Thomas Jefferson got obsessed with Elbow Macaroni specifically, and had the extrusion machines shipped to his property in the US while he was an ambassador in Italy.

He then created a simpler version of oven baked Mac and Cheese, and insisted on serving it at every formal dinner at Monticello, while he was president.