Nah, Parmigiano Reggiano is readily available in North America. You can buy them by the wheel at Costco if you're particularly crazy (and have a use for ~80lbs of cheese).
Ofc the cheap processed stuff is most commonly used, most Italian American dishes don't use real Parmesan, and stuff like Reggianito is cheaper (and also widely available) as well. But I assure you that I've had real Parmigiano Reggiano - and I've definitively used it in unorthodox ways :P
Now Casu Martzu you won't find in Canada or the US, because it's illegal to import. And TBH I don't feel like I'm missing out on that one.