I’m in EU and I have like 10 pizza places that deliver to my home, with multiple sizes to choose from. most even offer a gigantic rectangular party pizza: the biggest size that fits in the oven.

I’ve been at some Turkish snackbar/pizza place that offered three sizes: M, L and US. That last one was a family portion by itself, damn!

Though that still confirms that two to three slices being a single portion is a US thing.