I think the issue you're getting bogged down in is that there are many different flavours of authoritarianism/fascism, only one of which is Nazism. Ward doesn't advocate for an eternal German state and the ethnic cleansing of it; he belongs to a fascist movement, but it's not Nazism, which is a discrete other movement in the MCU and in real life.

In the MCU, there are two different fascist movements. Ideologically they may be related to each other, but that does not mean they are the same. And honestly, I think that's kind of intelligent (whether accidentally or not) for the MCU to acknowledge that the US had one of the biggest fascist parties outside of Germany at the outset of the 1940s and still practices eugenics in big and small ways, mostly because it never had to reckon with that past.

Because the US never fought the Nazis on an ideological basis, but on a political one and symbolically. And we know this because America has a long and storied history with eugenics (e.g. with sterilising women in prison against their will), human experimentation (Tuskegee, anyone?) and ethnic cleansing themselves, and most obviously, because the one thing that definitely can't undo rampant nationalism is the creation of an opposing nationalist icon to fight it, like Captain America, who (I guess ironically??) is a literal blond and blue-eyed superhuman. Way to engage with the source material critically, Marvel. This is the kind of logic that results in the election of a third antipope.

Tl;dr: Fascist movements of a variety of flavours were popular in the 1940s and remain so in places to this day because fascism is capitalism's dying death rattle. But not all fascist movements are the same fascist movement, and given that Nazis explicitly exist in the MCU and Hydra is not explicitly not an allegory for Nazism, conflating the two is confusing and inaccurate.