Without WAllied support the Soviets would have lost. We provided most of their quality steel, a good chunk of their aircraft, food to keep the Red Army from starving, rails to keep their railroads functioning as well as thousands of locomotives, molybdenum to harden the armor of their tanks, thousands of tanks, thousands of halftracks, tens of thousands trucks that were far better than anything Soviet factories could produce. We pulled thousands of artillery pieces away from the Eastern Front to defend Germany from our bombers and millions of men to man them. We pulled almost the entire Luftwaffe fighter force away from the Eastern Front and killed most of its experienced pilots. Boots, uniforms, radios, radar sets, artillery ammunition, fuel of all sorts, you name it and we gave it to them. The Soviets couldn’t even feed themselves without US support, oh yes I almost forgot about the millions of tons of fertilizer and pesticides. About the only things they made in quantity were direct warfighting objects like tanks, small arms, aircraft and artillery pieces.
Leg infantry on a WWII battle field were nothing but POWs waiting to happen. During Barbarossa the Germans captured millions of Soviet leg infantry because they lacked the mobility to avoid encirclement by mechanized forces. Without the tens of thousands American trucks, the Red Army would have been as immobile as it was in 1941.
And finally the WAllies forced Germany to pull at least a hundred divisions off the Eastern Front to fight in France and wear out their elite Panzer and Panzer Grenadier divisions shuttling them to the Western Front and then right back to the Eastern Front. A lot of the force the Germans used on the Eastern Front were from client states like Hungary and Romania, they had to use real German units on the Western Front because client troops would simply surrender knowing the WAllies wouldn’t shoot them and would treat them well.