Cold War era propaganda revisionism and Western Bias.
You hit the nail on the head in my opinion.
Of course the Cold War revisionism (denialism?) starts with never actually prosecuting Hirohito, Shiro Ishii (!), and the like.
Of course the myth is that the Japanese surrender had everything to with the US nukes and nothing to do with the Soviet Union invasion and that the Emperor was a figurehead who had nothing to do with the war. It worked out well for the emperor and the US. The irony is that the deadliest one day bombing of a city in world history was Japan in 1945, but Tokyo with conventional weapons. The nukes just didn't have the impact we like to imagine.
