The USSR has been given a huge share of the victory with revisionist history. Yes, they did a lot. A LOT. But they fought on one front and in one style of combat. The Eastern Front. They lost so many people because they were under supplied and sent hoards charging German machine gun nests with no weapons. The battles were huge and the costs high and they did a great job eating up a lot of German resources and men. Without the USA and England, Russia would have lost.
The USA fought on all fronts, as did England... almost. The USA supplied the world's Allies with everything and enabled both the UK and the USSR to survive. The USA fought naval battles, beach invasions, deserts and the bulk of the bombing.
England also battled in various theatres of war.