The US lost about 400K troops in WW2. The Soviet military and civilians who stopped the Nazi push into their country (stupid decision on the part of the Germans, btw) lost an estimated 20 million of their compatriots. For the US to pretend that they alone heroically saved the day is imho not only historically silly, but incredibly disrespectful of the desperate heroism of the defenders of Leningrad. American civilians sat home and read the news; Russian civilians fought and starved. We don't have to approve of Stalin to admit that credit for defeating the Nazis should be honestly and generously shared.
The US came in late, and was still doing business with the Nazis very late in the game; Hitler had a portrait of Henry Ford on his office wall and IBM Hollerith machines were used for the German census (part of which was about counting all the Jews and Gypsies) as late as 1941. Henry Ford's antisemitic rants from the Dearborn Independent (a newspaper which he conveniently owned) were anthologised in German translation in four volumes under the title "The International Jew, The World's Foremost Problem." The US role was not unmixed. There were ambiguities and contradictions. Americans played a role in enabling the Hitler gang, as well as a role in defeating it.
As in the UK, a small but vocal (until the direction of the war became clear) minority in the US was sympathetic to the Nazi cause. All that their friends in Germany asked was that they work to delay or prevent America's entry into the war on the "wrong" (i.e. anti-Nazi) side. This they did, arguing strongly for isolationism, "America First," and so on. I think it's disingenuous and ahistorical to claim that Americans would now be speaking German if the US hadn't rolled up its sleeves and punched out the bad guys; even Hitler, megalomaniac that he was, said that it would be nearly impossible to invade and subdue America, it was just too big. (And this from the guy who thought invading Russia in the winter was a good idea!)
Anyway, I do think it's time for Americans to get over the comic-book version of their role in WWII as some kind of Captain America superhero zooming in to Save The Day. They did bring tremendous wealth and materiel to the fight, and their troops fought bravely and distinguished themselves all over the place. But so did everybody else, and everybody else was exhausted and near bankrupt by the time the US finally decided to join the party.
In the UK, there were many variants of jokes on the "over there" song -- the Yanks were described as "overpaid, oversexed, overfed and over here" etc. But sometimes, this list of adjectives also included "overdue." People haven't forgotten that... people outside America, that is. It took the US a hella long time to decide whose side it was on.
As to America not conquering its subjects, please don't make me laugh. Hawai'i was conquered at gunpoint. America's aboriginal people were rounded up, bounty hunted, imprisoned in gulags (aka reservations) far from their homes... A big chunk of America was built literally on slave labour... nah, empire is as empire does. Not that this makes the US worse than any empire before or since -- I don't believe the US is exceptionally wicked, any more than it is exceptionally saintly. In some ways it is and was more inflexible than other empires; in ancient Rome, slavery was a social or business status and had nothing to do with race. Once s/he had bought his/her way out of slavery (or been rewarded for service with freedom), a Roman slave could become a Roman citizen equal to any other. Skin colour mattered less in Imperial Rome than it did in 19th century America (or 21st century America for that matter).
Lastly we shouldn't conflate "anti American-exceptionalist mythology" with "anti American." There's plenty to like about Americans and America -- but that stubborn insistence on being a separate and superior nation to all others in history is not one of the likeable bits... in fact it's kind of ironically similar to the Thousand Year Reich mythology or the fond notion that the USSR was some kind of exceptionalist unicorn that was going to lead all the workers of the world into Red Paradise (ha!). Once we start insisting that we're perfect and can do no wrong, it becomes almost impossible to correct our course... and history is just full of icebergs a-waitin' for ships that can't or won't steer.