Spaghetti & meatballs
Spaghetti exists in Italy -- there's no denying that. Meatballs also exist in Italy, albeit in a different form: there, they're called polpettes, and range in size between golfball-sized and marble-sized (aka polpettines). But combining these two often disparate entities? That's something that was reserved for Italian-American immigrants, who, after moving to America, found an abundance of cheap meat, pasta, and tomatoes, and decided to make a meal quite a bit different from the stuff they had overseas in the old country, thus paving the way for some innovative Alka-Seltzer commercials.