US military intervention and economic uplifting are partly two different things.

I would limit this discussion to "how can a once poor country become an industrialized economy".

Since not all countries do this, the question is incredibly interesting. Perhaps I were too harsh but "US helped them" is not a satisfactory answer.

The fact that north korea is poor and south korea is not, is an interesting part of this puzzle as rare empirical sample of an area with roughly equivalent starting position well into modern history, and it should not be explained away by "because US duh".

I found "Why Nations Fail" an extremely interesting book pondering the puzzle of apparent differences in economic outcomes between countries and warmly suggest it to anyone interested in the topic. It's not really about state failure but about the bigger picture of what makes some states successfull (using the metrics of the author of course).