The question why there was no prosecution is a least understandable on the international level: The US made it clear ever since WWII, if there should ever be an American sitting in jail of another power than them to be prosecuted for war crimes, they gonna try to free him. Also, they aren't going to accept any verdict of an international court for war crimes, neither against the American government as well as the American individuals which committed them throughout the world.
This is their scheme, their doctrine ever since after WWII.