I recall Zhukov didn’t think they could have won without the Wests help in supplying things like Steel, regardless of machismo from later USSR leaders who claimed they always had it all under control. FDRs death was gravely mourned in the Soviet Union. Stalin praised the allies for distracting them with the invasion of Italy.

The USSR did the most in that war but they were not in fact capable of winning by themselves.

They would have won but it would have taken a little bit longer.Lend lease was only 10 % of Soviet materiel

The Americans had some resources the soviets were in short supply of so their impact was greater than them just contributing 10% of materiel. Also again, Hitler had a lot of resources tied up in the west because of the allies.

Germany got pretty close to Moscow. A little different of a tactical situation would have been a big deal in that theatre of the war.

> only 10%

That does not mean anything. A car's engine contains only 10% of the parts in that car.

The difference is mainland US was not at war. They don't have to worry about bombing and siege and maintain production.

But it was the shipping that was the bitch.