What could go wrong with finally ending entangling alliances, especially one against a country that doesn't even exist anymore?
What could go wrong with not being the world policeman?
What could go wrong with countries that support their safety nets because they use our military having to use their own military?
In terms of what is good for the USA, absolutely nothing!
Years ago I heard a story, and I cannot verify its authenticity so don't ask, about some third world country experiencing a civil war. And both sides kept fighting because both sides expected that any day the USA would intervene on their side. And the USA didn't intervene at all. Finally both sides stopped fighting each other, got mad at the USA for ignoring them, and threatened to sue the USA for not intervening. I suppose you think they had a case.