The view that the lend-lease saved the USSR is used by right-wingers. It's rather odd to state it as if it is an absolute fact.
"Nor was Moscow saved by war material from America. Almost none of the eventual $11 billion worth of American Lend-Lease aid to the USSR arrived in time to save Moscow. American assurances of aid may have made Stalin more willing to throw material reserves into the struggle for his capital after October. But all told, Lend-Lease came to only 6% of Russian war material, most of it coming after Stalingrad. The thesis of Russian primitivity is inconsistent with the theory that Russia was saved by importing huge amounts of American goods along thousands of miles of railway.
The war material with which the Red Army saved Moscow and the bulk of the USSR was produced at home."
(Francis B. Randall. Stalin's Russia. New York: Free Press. 1965. p. 281.)
Isaac Deutscher noted in his otherwise quite hostile biography of Stalin that, "One might sum up broadly that the fire-power of the Red Army was home produced, whereas the element of its mobility was largely imported." (Stalin: A Political Biography, p. 512.) So basically the lend-lease, if it played a vital role, played such a role as to allow the Red Army to enter Eastern Europe or something, which isn't quite what I think the capitalist powers would have wanted.
In Geoffrey Robert's Stalin's Wars (2007) we read that (p. 164) such support was limited from 1941-42. Thus, "Most of this aid arrived after Stalingrad, so its main role was to facilitate victory rather than stave off defeat." Lend-lease assistance certainly helped, and the Soviets didn't ignore it. "Towards the end of the war the Soviet authorities began to reveal to citizens the full extent of the material support they had received." Again, such aid helped mobility. I've actually seen it used as a condemnation by conservatives concerning FDR's conduct during WWII, that the aid allowed the "commies" to take over Eastern Europe.