To provide some supporting fires to one of Dayuhan's points:

FDR was absolutely against colonialism (though much of that was his hate of the way it served to exclude the US from participating in rich markets. During WWII FDR met with the leaders of Tunisia, Morocco, etc and sold "democracy" and "self-determination" to an audience buying "liberty" while Churchill sat there and stewed (no booze at the dinner may have been his chief complaint). FDR also went in great detail about the value of doing business with the US...

So, when colonialism expired at the end of WWII as we were calling for that to happen; there were also long suppressed populaces newly empowered by a modern info age standing up and making the cost exceed the benefit of such arrangements.

Similarly, at the end of the Cold War while Reagan called for the Wall to be torn down by Gorby, at the same time it was the empowered populaces of that info age that also actually brought down another empire that was no longer cost viable.

It is like if I had my kid say "abracadabra" while I push the button on my remote control. He may well think it is the power of his word that makes the channels change or the garage door open. The truth is another matter.