No one likes to admit it, because Liberals, Europeans & Communists all have a vested interest in denying the degree to which the US was critical, or in glorifying the USSR's accomplishment. Neocons don't want to admit that any US military action was bad, and like to claim that we got involved in a European civil war in order to keep Stalin off the English channel, and other militarists had a professional interest in inflating the military threat of the Red Army.

The fact is, the Red Army never won a war on its own in the entire history of that abomination of a state that it served. It was really good at slaughtering rebels with no heavy weapons or air power, needed every advantage of numbers, wealth and equipment it could scrounge up to put down Finland, which had no modern military, got its ass kicked by Poland practically before that country was even a thing, and was humiliated in Afghanistan. They were taking casualties of 3:1 to 5:1 against Germany, even while Germany was diverted by the Western and African front, and didn't really load up for their initial invasion. Even with the flow of US & British supplies, the USSR might still have gone under if they had to face the Wehrmacht alone. If Germany was at peace with England after Dunkirk, they would not have needed to invade Crete or support the Italians in Africa, and they would have had Rommel and Student in action in Barbarossa. Imagine Rommel and the Africa Corps guarding the 6th Army's flank at Stalingrad, or the Fallschirmjaeger dropping on the Maikop oil fields, while the Bismarck & Tirpitz shell Archangel & Leningrad, and all those planes that went down over England are instead interdicting Soviet supply lines. We'd have Democrats today whining about Trump's alleged ties to Fuhrer Vladmir Putin of the GDR, for one thing.