In his original Marvel lore, Captain America was a key figure throughout World War II and after, but once he ed the The Avengers after being released from a block of ice years after being trapped in the ocean after a drone plane sacrifice.
Since the character has been literally and figuratively revived by Marvel Comics, his wartime morals have continued to be challenged and re-contextualized in new stories and the MCU's movie adaptations. However, one idea that's less frequently explored is the effect losing such a cultural icon had on the events of World War II. Cap changed history by fighting for his country, but he also changed it through how he died.
Avengers (2010) #2 by Brian Michael Bendis and John Romita Jr. finally answers that question during the "Oral History" portion of the issue. Nick Fury explains that Steve Rogers' death managed to galvanize American soldiers during World War II single-handedly. Rather than lower morale, his demise did the opposite for his fellow soldiers. In Fury's own words, the death of Captain America gave the armed forces, "a focus and direction that absolutely turned the tide of the war." Fury makes it clear that in a world with evil geniuses and Hydra's advanced weaponry, the Allies would have lost WWII if not for Steve Rogers' ing.
To finally get some context as to how Captain America, and specifically his death, helped swing the pendulum of the war within the Marvel Universe is fascinating enough. To find out that he swung the pendulum just as effectively, if not more so, in the wake of his death adds entirely new layers to the Marvel Universe. Particularly, new layers regarding an unseen chapter in the life of Steve Rogers. Fans take it for granted that the Nazis lost World War II because that's what happened in the real world, but if Fury is correct - and he has an unparalleled firsthand knowledge of history's battles - then it was only the sense of focus leant by Cap's death that meant this happened on Earth-616. Once it's taken into that the Red Skull, the original Baron Zemo, and more were developing super-weapons and superpowered humans, it makes sense that something extra was needed to achieve victory.
In real life, readers have seen, on more than one occasion, how the death of a leader, (be it in war or otherwise) can damage morale for anyone who follows them, often in ways that lead to serious consequences. It would be believable if the same was the case for the death of Steve Rogers in the middle of the war. Miraculously, the exact opposite was the case for Captain America's disappearance, as his 'death' is credited as the reason for winning the war as well as allowing him to later save the world at the side of the Avengers.
