If both Britain and the USSR were defeated by the Nazis in WW2 what would have happened?
The Cold War.
USA vs Germany.
Might not have stayed cold though.
Japan is an interesting one though, might have had WW3 with Japan backed by Germany and China backed by USA.
Would Mao have won the Chinese civil war is an interesting question in this hypothetical alternative future?
In a sense they've already won the war 73 years on. The idea of a European Union came from two SS guys, after Germany lost the war they gradually turned that idea into what the Nazis were trying to achieve through violence. Ironically it's the same brand of far-right that now forms much Euroscepticism on the continent...
Some things at a glance:
1. Hitler had plans to kill all the intellectuals in Britain so that there would not have been anyone smart enough to formulate an uprising against him.
2. On top of Jews, he was already killing vast numbers of people for being disabled, belonging to ethnic minorities or for simply not supporting him (and these killings would have continued to have escalate had he won).
3. He agreed with all this Aryan Race BS and there were plans to make it law for German citizens bearing Aryan features to have a minimum of 6 children per couple (basically if they were blond & fair etc, German men and women would have been forced to have lots of children). The Nazi's weren't just coming up with new architecture and breeds of animals etc to fulfill their Aryan vision, they were even intent on populating their new world with a perfect race of people. Couple's for this Aryan Race program would have been selected by the authorities (and people selected would have had no choice in the matter).