"Pies" is most certainly not American. I have heard that it is supposedly specific to New York, but if you watch Friends (set in New York), you'll see frequent references to the Joey Special, "two pizzas".
It's always possible that there are zero people who think of "pies" as an appropriate way to refer to pizzas, but the myth persists that weird foreign people do it. People will believe anything about weird foreigners. Or there might be weird foreign people doing it right now. It's hard to know.
Not? I'm confused who you're saying does call pizzas 'pies' (or 'pizza pies') then?
I assure you some Americans certainly do, wherever they got it from, 'American' or not. I've only been exposed to it via American film/TV, including food shows - most recently Somebody Feed Phil in Chicago.
I've never heard it in the UK. I'd be surprised to learn that Italians call them something else too that in other contexts translates as 'pie', but I'm not sure how relevant that would be anyway.
> I'm confused who you're saying does call pizzas 'pies' (or 'pizza pies') then?
I'm not saying anyone does that. I said so in my comment just above you. If I knew there were someone doing it, it would be hard for me to claim it was possible that zero people do it.
You've never heard it in the UK. I've never heard it in the US. It's not a normal thing to say. None of that adds up to a claim that some people say it.
Ok well I am claiming some American people do say it. Neither of us can speak for the entirety of our respective countries, but certainly I have heard Americans saying it on television and film.
In addition to the TV citation I gave above, see Wiktionary:
It's always possible that there are zero people who think of "pies" as an appropriate way to refer to pizzas, but the myth persists that weird foreign people do it. People will believe anything about weird foreigners. Or there might be weird foreign people doing it right now. It's hard to know.