The popular cultural myths are really just propaganda, the Lend Lease wasn't as large or as meaningful as is claimed.

Don't know which claims you're referring to, but if you like you can take the matter up with Khrushchev, Zhukov and others directly:

    I would like to express my candid opinion about Stalin's views on whether the Red Army and the Soviet Union could have coped with Nazi Germany and survived the war without aid from the United States and Britain. First, I would like to tell about some remarks Stalin made and repeated several times when we were "discussing freely" among ourselves. He stated bluntly that if the United States had not helped us, we would not have won the war. If we had had to fight Nazi Germany one on one, we could not have stood up against Germany's pressure, and we would have lost the war. ... He never made a special point of holding a conversation on the subject, but when we were engaged in some kind of relaxed conversation, going over international questions of the past and present, and when we would return to the subject of the path we had traveled during the war, that is what he said. When I listened to his remarks, I was fully in agreement with him, and today I am even more so.