There's no rule - I've seen as few as four slices on a large pie I see 6 or 8 commonly, but sometimes 12 or 16. You might have to ask for 16, I usually only see that when someone orders pizza for a meeting or something. That's the only time I see a round pie cut into "squares" too.We don't really have many different styles in terms of the crust, but the toppings are where the variation comes in. Most of the pizza here is "thin crust" although none is really as thin as NY style. There is some pan pizza. It pretty much all gets get like slices of pie, with an exception or two I'm sure.
Do they cut it into 16 slices up there? I hated getting pizza out in CA when I was living there. I actually used to insist that they cut it into 8 slices at the one Papa John's. Ocho? Si, Ocho. No mas. Ocho.