Those parts of the empire that did not engage in a fight to the death were given up under duress because of Roosevelt's and Truman's own imperial ambitions and the UK's absolute weakness when faced with the power of the US in the aftermath of WW2.
To be fair to Roosevelt, he warned Churchill that the price of US support (bearing in mind the aid we got before the US entered the war) was the loss of Empire. He was quite blunt about it - the American people would not support anything which looked like the US returning Britains empire to it. Hence the undignified end to the war in the Pacific.
Whether or not the mechanism of British government was transparent with it's subjects on that matter is a different story.
It's interesting to speculate what would have happened had the public been better informed about what they were actually losing sons, brothers, fathers, sisters, mothers and children for ?
It's the same climate of ignorance that prevailed during the troubles.
Fans of supersonic passenger travel and transparent government might be interested to know that the US government was approached when Concord was being developed (because the UK desperately wanted to work with anyone but France). The US government pretty quickly sized up the situation and declined. As one official said in an interview:
It would have been politically impossible for the US government to be seen subsidising a program which was mean to see rich playboys jetsetting around the world with US taxpayer dollars.
I mention that, because it highlights a fundamental difference between the US perception of it's people, and the English perception of it's people.