Man do I ever love pizza, I love it so much that I study it for a living, IS there anything you'd like to know about it? 
Yeah where did pizza come from?  Is it an american food?
Pizza actually was first recorded in the early 10th century, in a Latin manuscript to originate from a very small Southern Italian town called Gaeta in Lazio, located close to Campania.
Oh wow! I didn't know pizza was that old! I know I love cheese and pepperoni, but what's the official definition of pizza?
Well pizza itself is just an Italian dish with yeast flatbread usually topped with tomato sauce and cheese and baked in an fiery hot  oven.
Ok so it's pretty basic.  Are there any major differences between pizza in the U.S. and pizza in Italy?
Not really buy ever since the introduction of pizza brands like Domino's and Pizza Hut, it has reached almost all classes of urban peoples. So its everywhere nowadays, And is more american.