I don't know where Hollowood ever said it WW2 was about Jews.
IDK if things have changed but generally the whole narrative in the US is presented as unwitting yankies discovering the horrors of the death camps. It's debated how much some levels of the government knew, but it certainly wasn't public knowledge in the US.
Well, that or fighting the Japanese.
There was definitely some knowledge of how Jews were being treated by Germany very early on, and some people were very vocal in condemning it, although they cleaned up their act during the Berlin Olympics. The Holocaust really seems to have escalated during the war itself, and with the invasion of the USSR. By this time the British Empire was already at war with them.
Patriotism and threat seem to have been the main motivators for most people in the west.