I traveled a lot and I know there are many Italian restaurants outside Italy that has spaghetti and meatballs on their menu.
But ask a waiter in Italy for such a course and he will just stare at you.
Even if you practice your best Italian and ask for "spaghetti con polpettine" your request will be denied.
Meatballs are just served as a side dish, they aren't served with spaghetti, but I can still remember my mother doing such pairing when I was a kid. She used to serve us such meal yes, it's more traditional homemade dish rather than restaurant one.
Because it's not served at restaurants some Italians and
Italian-Americans have come to believe that it's not an authentic
Italian dish. Well with your suprise I asked my mother and got the recipe below, though the meatballs are made separately you'll find here the recipe to follow.
Freshly grated Parmiggiano Reggiano gives all another taste to your pasta dishes. Use a rotory cheese grater, don't buy pregrated cheese, it dries out and loses much of its flavor.
Serve immediately with grated cheese!