While it is true that Soviets did a major part of the actual combat work, they probably could not have done it without economic help from the US. If US were unable or unwilling to provide such help, it is not at all given that Soviet economy alone would have survived the onslaught. While the heroism of the Red Army people is unquestionable, one needs a lot of material resources to wage war, and without them even most heroic people can not win. Even Joseph Stalin - a man not known for being overly modest - acknowledged that.

https://en.wikipedia.org/wiki/Lend-Lease