Britain won WWII at the cost of its entire empire.
Germany was down to old men and boys in the Battle of Berlin.
So many Russian men died in WWII, its demographics suffered a ripple effects for years to come.
Japan resorted to suicide bombers.
France...well France had gone through a terrible experience in WWI and can't really be blamed for bowing out when it did.
But the United States barely broke a sweat. It fought a two-front war and had enough resources for the Manhattan project left over. It then went into a 40 year Cold War and outlasted the U.S.S.R.
What does a U.S.A. that threw absolutely everything it had into WWII or a war that occurred in a similar timeframe? If the United States fought a war that directly threatened the existence of the country in the same way WWII threatened the very existence of Russia, etc. Whether that war is against a Nazi Germany that won in Russia, or against the U.S.S.R. in the days shortly after the end of WWII. The POD can be quite early, even early enough to make a successful Sealion. The key thing is that at some point in the war, the U.S. is pushed as far as it can go as far as resources and manpower goes. What would the army, navy and airforce of this alt-U.S.A. look like?