I'm really, honestly curious what reasons you have to believe this. I can't imagine any. It is so much different from my view and the view of the people I usual

I'm really, honestly curious what reasons you have to believe this. I can't imagine any. It is so much different from my view and the view of the people I usually talk to, that I can't fathom where it comes from. Is it something you read, something you saw on youtube, your experience travelling to some countries? How do you base your assertions? I'm honestly lost and I'd like to understand. How can you assert that "Pizza served all over the world is based on the American Pizza, not the Italian one"?