Pizze may be Italian, but pizzas are not. Times have moved on. I
recall, many years ago, walking in Rome and seeing the following sign:

Pizza Americana! Qui! Oggi!

This Pizza Americana was a typical thin-crust Pizza Hut kind of pie.
Whether because of America's chain pizza vendors or because pizza
simply lends itself to innovation, it has become completely
cosmopolitan these days.

And while I cannot answer your question about the Hawaiian pizza, I can
offer this additional bit of signage, observed outside a west-coast US
pizza restaurant:

Help Wanted. Large Hawaiian $6.99.

It didn't seem like they were paying very much for such specific
requirements...

Skep