Until very recently, Italy’s source of wheat for most of its pasta flour and a lot of pizza flour has traditionally been North America. Our winter durum wheat has the right proportion of protein, and because of climate they can’t grow enough of their own. (This has all changed recently because of new Italian country-of-origin labelling laws and a new Canadian-European trade agreement.) So the flour isn’t “better” – it was the same flour you had in your cupboard at home.
I’d say with pasta and pizza the biggest difference is portion size. An Italian portion of pasta – usually a first course and hardly ever seen as a main course – is nowhere near as huge as a North American main course serving. And as @Chris says, they don’t load their pizzas with masses of (generally flavourless) cheese and several kinds of meats.
Plus, when you’re travelling, you’re generally more active.