'Afghanistan' is barely a state, it never really was a nation. It's a 'border' around a chaotic gaggle of tribes living in the past. They'll ebb and flow given different kinds of leadership, most of which won't have anything to do with anything happening outside urban limits anyhow.
Iraq was a deeply corrupted and broken state, again, difficult to rebuild to, but possible. Absent ethnic tensions it probably would have gone a little bit better, and paradoxically, US forces were more of a stabilizing factor than not. Literally the day that US forces withdrew and US lost it's leverage in Iraqi politics, PM malaki basically launched a kind of political civil war. That scared the Sunnis who 'allowed' ISIL to come in, believing they were a better option than the Shia dominate government, unrestrained from American influence.
S. Vietnam was a bit incoherent, but it could have worked fine were the US to have been able to provide security. They did not, largely due to the historical insanity of refusing to attack the North. As Op. Linebacker I and II eventually demonstrated (but way too late), North Vietnam could be handily decimated at will with direct strategic bombing. Were those ops to have happened in 1965 instead of 1972, the war would have had a different outcome. It's unlikely that S. Vietnam would quite look like S. Korea, but it would be more like it. Instead, we have an ultra authoritarian entity that did some vastly horrible things in the past, but which has settled down a bit in subsequent decades.
'Marshall Plan' works where the Marshall Plan can be taken advantage of.
The IMF has tried similar things elsewhere after WW2, it didn't work out so well, because, well, Nigeria and Indonesia are not at all like Germany or Japan.
Russia has been 'backwards' forever, it's like part of their identity to be 50 years behind everyone but still antagonist about it i.e. aggressors and victims at the same time. I can't see how it will change.
Russians will happily exchange their own prosperity to save face to themselves, and live in a kind of delusion of their own making. They will literally lose the war in Ukraine, but believe they have 'won'. They will declare Ukraine 'denazified', have a parade about it, and 50% of the population will fully believe it, the other 50% will know the truth and go about their daily business, unable to really speak publicly about it.
South Korea has recieved as much ecobomic aid as all of Africa combined in the 20 years after its formation.
Arguably Kurds should get their own territory.
Afghanistan and Iraq are weak states dominated by sectarian violence. Vietnam is and was a strong state.
The US had the power to dictate whatever terms.
Japan was on it's back.
Russia in 1992 was it's own entity. Still a nuclear power. Making it's own decisions.
Not only would Russia not have tolerated US intervention, I'm extremely doubtful there could have been such a thing on any terms.
As it stands, much of the money used by Oligarchs to buy up Natural Resources firms was from the US private banking system.
Russia is Russia, they are 100% responsible for their own problems, and those have been roiling through history for 100's of years.