Germany would have won, Japan may or may not have.
Russia was kept alive by American lend-lease. If "the USA staying out of war" means no lend-lease, Russia would have been ****ed and the rest of Europe with it.
Japan was in a very crappy position resource-wise. There's a great chance they would have overextended themselves on China and India and ended up failing, or only securing part of Asia.
If Germany won, they'd have likely heavily depopulated and colonized the Slavic world until Hitler's death, upon which the system would either explode spectacularly or stabilize into a thriving long-term empire. Britain would remain independent, since Hitler didn't really want a war with them and didn't have a navy capable of pursuing an invasion anyways.
Communism is discredited and Fascism becomes a world ideology (even in the US, in my opinion) in such a scenario.
EDIT: The post-war collapse would be due to a nutjob replacing Hitler on the terrible administration of the Nazis finally leading to something like an economic disaster, while the thriving empire would be due to a moderate reforming the system and using raubwirtschaft money to keep the economy chugging until it can stand on its own two feet. Now, Franco was never in charge of an extremist state, but the reason I think Nazi Germany could possibly be reformed is that we have a practical example of that in the form of Francoist Spain (went from Falangist to traditionalist and then capitalist).