reposting what I've said about this before:

the US was the only country on earth that had nukes for 5 years and was unscathed from WWII. We could have demilitarized and enslaved the entire planet under threat of nuclear death, but instead we gave away billions to help Japan and Europe rebuild. There's never been a more selfless act in human history as far as a country not seizing an opportunity to gain power is concerned. There's probably never been a larger power disparity between a single country and the rest of the world than post WWII USA, and they did exactly nothing to take advantage of that disparity.

US is far from perfect, mainly due to unconstitutional actions by our intel community and military, but as far as superpowers go there's really no comparison.