1. There is more than one kind of pizza
Pizza is originally from Naples, Italy. Napoletana style pizza isn't something you see very often in the USA, unless you're lucky enough to have a local pizzeria that knows their stuff. Napoletana style has big fluffy crust with pieces of white mozzarella and a more soupy tomato sauce. It is a very light pizza though, eating the whole thing isn't that big of a challenge. In Rome many places cook their pizza in a square pan and serve by the slice. They cut the slice right in front of you and you will pay based on how much it weighs, you can get amazing pizza very cheap this way. Also, many restaurants offer pizzas very similar to New York style, a flat crust pizza with a coat of mozzarella. Every type is good but the Roman slices are my favorite.
Here is a video from a well known Roman pizzeria. You can see them cutting a slice with scissors!
2. Every pizza is a personal pizza
In the USA we consider pizza a family dish where everyone takes a slice and eats but in Italy you get the whole pie to yourself. Eating it with a fork and knife is perfectly ok, too.
3. Pizza can be found in almost every restaurant...
... and it's usually the cheapest part of the menu. You get a ton of food for not a lot of Euro, and it's very good generally as well. Enough said.
4. The calzones are awesome
They're sometimes called inside out pizzas, I grew up eating these in America and even though they are mostly the same in Italy, the Italians still do it better. Mostly because their Ricotta cheese is vastly better to any I've had in the States. Also they give a different experience than eating a regular pie, if that's what you need.
5. Italians aren't purists about their toppings
But they do have good taste, and so should you. You simply can't beat a piece of pizza with a slice of prosciutto on it. Leave the pineapples for you pina colada.
6. White pizza is more common in Italy
And it's actually pretty good, I say that as someone who thinks the best part of a pizza is the tomato sauce. In my experience these pizzas tend to pick one flavor and stick with it, rather than a huge collab of ingredients. Just like how every dog has its day, white pizza hits the spot when you need it.
7. Good pizza can be found in the USA, too.
Lots of people like to disparage American pizza as being inauthentic, gross, or just plain wrong. That's not always true though, there are lots of pizzerias owned by families that make great food worth your consideration. We do things differently here but that doesn't make it automatically bad.