First, I'll answer the post ipso facto aspect: The USA did meddle, and was that good? In the case of Pinochet, no, because he was a brutal authoritarian and was obviously the worse alternative to the leftist, not even communist, government he overthrew. Also, if the people voted for communism, then, that's self determination, let them have it. If it works, it works, if it doesn't, it doesn't, that's no business of America's. A military coup is "might makes right," an unethical ideology. So if we compare the two forms of meddling, actually, the USSR's was more ethical, since it was aligned with the will of the people. Overall though I still think neither country should have meddled.
What should have been done instead? If the USSR is meddling, the USA as a nation state should do nothing more than leverage its platform to expose any instances of meddling, especially if they were against the will of the people (e.g. fraudulent votes). The people in the USA is a different thing entirely, if I knew what direct action people could take to resist nation state meddling entirely I'd write it here, since I don't, I'll just say the usual: form subversive relationships with neighbors in opposition to authority, mutual aid in opposition to capital-derived infrastructure, mutual education, mutual bonds.
As for Hitler, who also rose to power undemocratically I might add (Reichstag fire and the like), he was committing a genocide, any and all means to stop that is ethical, including full invasion by other nation states. On the other hand, I can't think of an ethical way for a nation state to prevent him coming to power. After all, at the time, I'm not sure it was possible to predict what he was about to do - an anti-semitic politician wasn't exactly groundbreaking, and nobody had ever seen a Holocaust before. If Germany can't prevent itself from becoming a fascist hellhole I don't really see America's responsibility there other than to offer safe haven to any fleeing Jewish people, gays, trans people, communists, etc. Since time machines don't exist, I can't think of an ethical justification for USA meddling in Germany pre-Holocaust or pre-invasion of Poland.
What do you think? I think an interesting question is, "what is ethical and allowed if Hitler 2 arrived today and began seeking power?" Such questions could have interesting answers depending on what you think America should be allowed to do to the current person and nation conducting a genocide, Netanyahu in Israel.
> It sounds like you’re backing away from meddling is always bad?
No, they just never said that in the first place. What they said was, "Yes, the USA shouldn't be meddling in the domestic affairs of other countries to action its proxy cold war against a rival super power." Emphasis mine.
