Really? Are you trying to say that without US involvement Hitler and Japan could have been defeated? First without US involvement in Africa Hitler would have controled the Med and we would not have been able to attack from the west. Without our being able to open a western front the Russians would have been defeated. Without our defeating Japan, the Russian eastern border was threatened along with the Japanese holding China and taking over SE asia, Australian, NZ , Malasia and on and on. Without the materials and equipment supplied to Russia by the US Russia would have fallen quickly as would have the UK.

And of course we managed to put together the atomic bomb which save millions of lives in the end and put a final stop to it all.

Success? HUGE success. Joint effort, by far. Too bad the jealousy and ego of the rest of the world prevents them from helping in the current situation and the US has to go it virtually alone.