Hot dogs/weiners/frankfurters are German in origin.

Hamburger is also German.  Yes, the “hamburger sandwich”  (the hamburger served on bread) is American, but at its core…. the ground beef …. is originally a German concept. 

Pizza is originally from Naples, Italy.

How about potato chips?  Not a “dish” per se, but a national food.   Maybe it would be the national snack.  It is a 100% American creation from Saratoga Springs, NY.   Potato chips are everywhere in the USA, eaten by almost every American, and not super common in other countries. 

Glenn

Points well taken. 
So, it looks like Eastern Carolina whole hog barbecue is [:p][:p]IT[:p][:p]!
 
(And I couldn’t agree more.  Thank me very much.  Pass the spicy vinegar sauce, please.).