You are kidding about C. America, and South America too?
Communism in Argentina? When?
Allende in Chile was left wing true, he was also elected.
In any case, much of the worst US behavior in that region was before the Cold War, before WW2.
It led to the situation in the 70's/80's, when Guatemala, run by a truly vile line of dictators, originally installed by the US to replace an elected government, was threatening the British Dependency of Belize, it got to the point where troops, helicopters, surface to air missiles, a warship and a flight of Harriers, had to be maintained in Belize, to ward off a regime supported by the US!
Communism didn't enter into it, if a major NATO ally thought that this was not an issue, why did the US?
Only years after Belize went independent, once that threatening regime was gone across the border, did UK forces withdraw.
Then there was the marked lack of support for several weeks at the start of the Falklands crisis, that some in the US government even considered the regime in Argentina as worthy of support was very telling, the US came round in the end, after the Junta were proved to be a bunch of drunken thugs, as Al Haig found out first hand.
Also, Weinberger warned that if Argentina got away with it, one result could well be that Thatcher would be out of office, replaced by a Labour Party that was then anti nuclear, all US and UK weapons gone from UK soil, really anti any US bases being here, anti NATO too, so coming on our side eventually was not a 'Special Relationship', just what's better for the US.
Vietnam was a French mess true, but they got out, all the US did was prop up regimes in the South every bit as brutal as the North, only more corrupt.
In WW2, Giap's forces often aided the escape and evasion of downed US aircrew, he was feted by the US in the immediate post war period, which encouraged him to move against the French.
France has a funny relationship with it's former African colonies, they largely did what we did on withdrawal, but they've been more proactive in trying to put things right when it's all gone to shit out there.
Are they right? I don't know, should the UK have overthrown Idi Amin for example?
Whatever you do, your dammed, either for neglect or trying to 're-colonize'.
We did consider overthrowing Ian Smith in Rhodesia, when he declared independence to pre-empt the UK insisting on Majority rule, i.e. letting the Africans and not just the colonists vote.
Instead, he was embargoed, the UK was the first to ban arms sales to South Africa in the 60's, a decade before the rest of the world.
But today, you have Mugabe destroying his nation, he partly gets away with it as he knows how to play to the gallery citing 'White Colonlism'.
Bravo to anyone trying to do something, but Sudan?
Really, this is one for the African Union, they are in Sierra Leone now, but only after British forces stabilized the situation in 2000 and got rid of one of the main insurgent groups.
Sudan was a UK colony, now Blair did make noises about sending troops to secure aid, only to get a rebuff from the AU
So saying 'something should be done' is the easy part.