re: Would the Allies have won WWII without America getting involved?

Could the Allies have won WWII without the USA's involvement? In a word, NO. I say that because before we shot the first bullet in battle the US was supplying the UK and others with weapons and supplies that helped keep them in the game. And b/c Britain wouldn't cave in or negotiate a treaty with Germany Hitler got antsy and turned his attention to the USSR (non-aggression pact partners) and made the BIG mistake of invading them before England was dispatched. Then enters Japan and Pearl Harbor and we got in it.
The revisionist PC party line has of late over- tipped the hat to the Soviets for doing a lot of the dirty work along the Eastern Front - but once again the US was providing much needed weaponry and supplies to the Ruskies which also helped keep them in the fight - not to mention the actual military involvement of American forces which kept the Wehrmacht busy in the West and prevented them from fully crushing Stalin. Divided they nearly did anyway.