Even thinking back to high school history classes we were taught that the US played a huge role in winning the war and if they actually didn’t, why is it made it seem that way? could the war have been won without US involvement ?
Possible? Yes.
Probable? No.
It would've been incredibly difficult for the Soviet Union or the British to win the war without US aid. The British Isles alone couldn't match the industrial output of Germany they desperately needed the North Atlantic trade routes to Canada and the Suez Canal just to keep fighting. But between the resources needed to defend the Suez and fight in the Atlantic, the British resources were stretch razor thin. Without lend lease aid like the Clemson class destroyers the British Navy probably would've lost the Battle of the Atlantic. Without the American aid in North Africa the Germans could've taken the Suez and middle east oil fields.
The Soviets themselves needed lend-lease material from the Americans. Early in the war they lost a vast amount of supplies and all the equipment needed to rebuild had to come from somewhere. Throughout the war the Soviets got 400,000 trucks from the US and almost half of the Soviet fighters came from the US and British lend-lease programs.
Further when you consider the allied bombing campaign against the Balkan oilfields and the strategic effect that had on the Germans, not only straining German oil production but perhaps more importantly diverting the German air force, away from the Soviet front.
When you consider the US went on to be a superpower following the events of WWII it really shows the economy of scale that had evolved. The US not only had built up enough matériel and financial resources to create their own massive military, they created one large enough to deliver significant amounts of aid to every allied country.