Perhaps I should have not used the term "working hard".
I agree with what you wrote in general.
Why I find other explanations more worthwhile - which you opened up above - than "US helped them" is that is quite critical for countries to be able to advance economically. Based on several examples I don't think it can be explained simply by having a wealthy external sponsor. Hence it would be more important to focus on the things that made this thing happen, in order to understand if something could be replicated.
As an example of potentially replicable factors, for instance land reform seems to be a thing that has been at the roots of economic advancement of several countries. (Finland, South Korea). Of course, it can be screwed up as well (Zimbabwe).
I agree books that try to simplify things are dangerous, but really entertaining when they structure their thesis around solid facts. I don't think anyone has "the final truth" so an author that has at least tried to put forward an explicit thesis is always a worthwhile read - a clearly stated thesis is something the reader is then able to clearly refuse.