It bankrupted the Soviet Union. The US private sector was able to develop the new technology and created new products and industries.
Faith in socialism, capitalism or communism prevents the rise of fascism because it combines aspects of these things but is different from them all. The idea that democracy is failing can help it rise. Hitler exploited the instability of Germany's democracy and the failure of the coalition governments to push for total power, presenting the idea that Germany needed a 'firm hand' for 4 years to get back on steady footing.
I believe that the United States had no imperialistic motives for entering WWII. Because Great Britain, Russia, and Germany all used to be empires at some point in their history, and they might have wanted to become empires again, whereas America had no such wishes.
