Popular Hollywood "history". It is a fact the back of the German military was broken on the Russian front at places like Stalingrad and Kursk. Yes, America contributed, no one is saying otherwise, but the mantra-like "America defeated the Germans for the rest of the world" is so erroneous as to be false. As well as ignoring the blunt fact that most of the fighting and dying was done by Russians, it also handily ignores the contribution of the other allies, particularly the British Commonwealth forces. There were 2 million Americans who served in Europe, Canada sent a million herself. Australia, with a population of just 7 million, had a million people serve in the military in some capacity during the war!
So yeah, America played a part, sure, an important part, no one is suggesting otherwise. But the John Wayne "America single handedly saved the World from the NAZIs" is bull****.
I don't think the claim is about America "single-handedly" saving the world from the Nazis.
Part of the reason why Americans are taught this decidedly pro-American view of history is so that the powers that be can appeal to American pride and patriotism so the people will continue supporting our militaristic policies.
The general perception is that many of our allies are so weak that they can't defend themselves, which feeds into the notion that American involvement is indispensable to world security. It puts an undue burden and obligation on America that "if not us, then who?"
On paper, Britain and France had Germany outnumbered and outgunned, so they should have defeated the Germans in 1939-40. The fact that they were defeated so quickly and so handily in the Battle of France made the Germans look unstoppable, in addition to making France and Britain look impotent. The first six months of Barbarossa also fed into this idea that the Germans were an unstoppable juggernaut.
And I reiterate, the Second World War was 80 years ago. Thanks for your contribution. But it's not a get out of gaol free card when it comes to the basic conventions of decency and conduct for the rest of time.
It doesn't lessen the perceived necessity of American involvement, though.
After WW2, being that we were still part of the Allies who were still facing problems on a global level, Americans felt obligated to continue to prop up the world system which had been previously managed mainly by the French and the British. This expanded the nature and scope of American foreign policy and security aspirations into areas formerly under Anglo-French control - in Southeast Asia, the Middle East, Africa - all of which were actively resisting colonial control, with the Soviets seeing an opportunity to fill the power vacuum that was left after WW2.
But even that's no longer relevant in today's world, so one might still wonder: Why is America still involved all over the world? Again, it's because of the ongoing perceptions that much of the world is still chaotic, unstable, and threatened by tyranny, while the so-called "good" countries are still viewed as too weak or short-sighted to be able to defend themselves. As a result, American involvement is deemed "indispensable" and "vital" to world stability.
Among Americans, there's a certain peer pressure and guilt complex at work, where failure to support American militarism is deemed "cowardly" and tantamount to turning our backs on innocent women and children being tortured to death. Those who oppose US militarism are often considered too naive and unaware of just how "evil" and "treacherous" our adversaries can be.