The most popular forms of pizza in the US (and the world, I believe) are called the New York style Pizza, the Philadelphia style pizza, etc.
The Italians exported the pizza to the US where it became popular, and from there, it was taken to the rest of the world. The biggest Pizza chains are all American - Dominos, Pizza Hut, etc.
The most popular form of Pizza in the World is not New York Style Pizza, that can only come from someone that has never been to Europe, Pizza is just called Pizza, nobody in in the rest of the world refers to it as "new york" or "philly style"...just because Pizza is popular in the US does not mean we exported it..thats (sorry to say) 100% nonsense...its very popular in the US, but its not considered American food...which is why restaurant even in the US that usually offer pizza are ITALIAN restaurants...