If Americans delete Italy they will be the Pariah of the world for a very long time
Pariahship only really matter if you care. Look at both India and China. For the past 80 years countries cared about being pariahs because there was only one real country: the United States of America. Today, there are a handful of truly sovereign countries (America, China, India, Russia, Ukraine, Iran, North Korea) who will actually defend themselves without resorting to nominal allies .
In the normal state of human affairs, being a pariah doesn't matter as long as your goals get done
Maybe, but it's still the reason Italy can't bomb America.
The rest of the world wouldn't do anything about it either, IMO. Just like they're doing for Ukraine now.