Comics aren't fascist, but they are authoritarian. Fascism is a very specific subset of authoritarian that is actually rather rare in comics, despite the word being misused often.

Comics are authoritarian because they are heavily inspired by Christianity, King Arthur stuff, Greek/Norse mythology, etc. None of those things have much use for democracy. All take this as a fundamental truth: that there is an objective morality, the protagonist can see it clearly, and everyone else is blind to it, including the masses. Democracy is synonymous with the masses. Comics are therefore far more comfortable with the Rightful King and his Paladins than Presidents, since the Rightful King and his Paladins can clearly see the one true morality, and the President is just the representative of mob rule and the blind masses.