For example, Panama, Chile, Germany, Japan, South Korea all turned out better after US intervention. But Afghanistan, Iraq and Libya got worse.
It is tough to choose the lesser of two evil, when you are in a democratically free country, you do wonder if the opportunity shows up, should you go help others overturn their dictator, and if so, will they then be able to establish a free democracy or will that just replace one dictator with a worse one? But what also happens is the fear, that if more and more countries lose freedom and democracy, and become dictatorships, then countries in free democracies get scared that they will be next, which tend to push them to act and try and overthrow other dictatorships when the opportunity shows up.
Just so you know, there used to be a single Korea. One of them is doing OK now, although it took like 35 years after the US invaded before SK transformed itself into a democratic country, which Koreans did IN SPITE of American support for their dictator. The other one is possibly the worst regime currently active on Earth.
South Korea is really not an American FP win.