Because those are the Italians I have experience with, and the Italian Sugo al pomodoro isn't to my knowledge ever cooked for hours. The slow cooked variety in Italy is the ragù which is cooked up to 4 hours. If you cook any tomato sauce much beyond 4 hours you lose the actual tomato flavor[1]. So I sincerely doubt forever tomato sauce is a real thing.

[1] https://www.seriouseats.com/the-best-slow-cooked-italian-ame...

> Aren’t Italian Americans just regular Italians

No. The term generally refers to a groups of people descended from Italian immigrants who formed their own culture in America that blended regional Italian languages and cuisines with local American ingredients, language and customs. The big pot of red sauce in question doesn't exist in Italy, it's an invention of early 20th century Italian immigrants to the US.