I've wondered about this ever since I spent a couple of days in Salerno a few years back, as a base for Pompeii & the Amalfi Coast.
The bulk of restaurants in Salerno were pizzerias, and they all served pizza that was akin to NY pizza--bigger pies and thicker crust than in most of Italy. They were similar to the kinds of pies you'd get at Lombardi's or Totonno's.
New York-style pizza is known as Neapolitan, but from what I understand the contemporary Neapolitan pizza is smaller & thinner crust (I've never been to Naples).
Salerno is not too far from Naples. I'm wondering if the Salerno pizza is a throwback to the 19th century Neapolitan style that may have been the inspiration for New York pizza, of if somehow Salerno adopted New York-style pizza more recently.
Any ideas, anybody?