The Cold War played a big role in downplaying and misrepresenting Soviet participation in WW2. The end of WW2 was already an uneasy alliance that pretty much immediately turned into the Cold War. It wasn’t too long after that when the Soviets represented an existential threat to the US, which Nazi Germany never did.
It was a time when we were paranoid about secret Soviet infiltrators every which way. About Soviet propoganda and ideology appealing to the whole world, including people here. And so very little would be said that put the Soviets in a positive light. It might even be considered, by the paranoid standards of the time, seditious.
And hence we were happy to downplay Soviet involvement and especially Soviet battle skill. Myths from that era are still strong to this day, that the Soviets were poor fighters, that they only defeated the German super soldiers through massive numbers - the popular belief in most of the West is a Soviet Union that just threw cannon fodder over and over again against Germans who were superior in every way but were just overcome eventually by the barbarian hordes.
That narrative isn’t entirely made up - the Red Army of 1941 was certainly massively outfought by the Germans. But very few people in the west who haven’t studied the war aren’t aware that the Soviets underwent massive changes in leadership, doctrine, and equipment as the war went on. By 1943, the Red Army was generally better at war fighting than the Wermacht. They didn’t overwhelm the Germans with numbers - the highest manpower advantage they ever had in the war was 1.6:1 - which is substantial, but not at all fitting the barbarian hordes myth.
A lot of Americans who learn more about WW2 than average tend to go through a Wehraboo phase where everything German is mythologized. Super weapons, super soldiers, super tactics - only to heroically come up short against the unending numbers of poorly trained and lead Soviet soldiers. I’m sure the West German soldiers at the time were happy to play into this myth, and certainly the cold war Americans were happy to downplay the threat posed by our new and powerful adversaries.
But it does a disservice. The ostfront was basically 80-90% of the entire war in Europe, with everything else being a sideshow. Americans seem to believe that we basically invaded Normandy and conquered the Germans at full strength after a few years of bombing, when in reality it was closer to a desperate attempt to free Western Europe before the Soviets decided they might just push on through until they reached the Atlantic. The war was already decided at that point.
Which isn’t to say that the American or Commonwealth forces weren’t important - American supplies really were crucial to the improvement to the Red Army’s ability to wage battle even as early as 1942, and defense against the bombing campaign as well as the Battle of the Atlantic consumed important resources that would otherwise be allocated to the eastern front. But in terms of the actual battles fought during the war in europe, nothing even holds a candle to the gargantuan struggle between the Germans and Soviets.