At their core, however, the classic superheroes work to maintain the status quo and support the existing power structures of when they’re written.
At no point did Superman or Captain America stop American forces from invading a foreign country for example, or overthrow a medical insurance company.
Did you miss the part where I mentioned the entire “Captain America quits because he thinks he can’t use that name while Nixon remains president” thing? Or the “DC makes Lex Luthor president during the G. W. Bush administration” bit? Captain America is such an easy mark for self-reflections on jingoism I feel he’s spent more time repudiating right wing conceptions of nationalism than doing anything else. “Cap fights right-wing take on himself” is such a trope that when they adapted it into the recent TV show fans spent hours debating which of the evil fascist Caps they were doing, especially since they had already done another one of them in Daredevil. And by the way, the whole “they were actually experimenting on black people first and then erased that from history” bit from that show? Also from the comics, but more recent. From… you know, the Bush administration.
And then there’s the X-Men, at least on their second run starting in 75, focusing on mutants as a pretty generic stand-in for discriminated groups, featuring a diverse cast and very much told from the perspective of the outsider. That went on indefinitely, all the way to having a (debatably handled) entire analogue for the AIDS crisis be a core ongoing plot thread for years. Alan Moore, who isn’t particularly right-leaning, also spent a whole stint at DC in the 80s turning Swamp Thing into an environmentalist free-love counterculture icon. I say “turning”, but the original run wasn’t particularly “uphold existing power structures” either.
At the core, episodic media is episodic, so it tends to return to status quo both as a political statement and as a storytelling device. And of course, censored media, be it Hollywood movies under the Hays code or superhero comics under the Comics code were subject to strict limitations. But there have been pretty out there superheroes since day one (cue kinky Wonder Woman backstory here).
Again, books are books, and fiction often depicts the positions of its creators. People like to consolidate genres or styles into single ideologies, which is normally and obviously reductive.
You can chip away at counterexamples all day. Deconstructionist superheroes don’t count. Pre-code outsider stuff doesn’t count. Specific one-off statements don’t count. Modern progressive takes don’t count. What that gets you is that conservative comics are conservative, which is obviously true but isn’t much of an analysis.
And you missed the point of asking what Captain America did to ensure someone like Richard Nixon couldn’t get elected again. Or Superman with Lex Luthor.
Of course there are other examples of progressive comics, but the mainstay superheroes aren’t seen leading revolutions or improving political systems. They’re working against change.
Except when they aren’t. Again, you can ignore all the counterexamples you want, nothing is keeping writers away from whatever subtext they want to give. Alan Moore wasn’t any more conservative writing Superman than he was when having Swamp Thing take down corporate stooges in the name of “the Green”.
And of course there’s a TON of deconstruction happening for many decades. I’ve been holding back from pointing out The Dark Knight Returns presenting Superman as exactly what you claim because Batman as libertarian revolutionary isn’t exactly an example of progressivism, but “Bats goes fash” isn’t a one-off. At one point he destroyed the world by giving in to global surveillance.
Oh, and Wonder Woman killed the head of a US spy agency just after that. On live TV. Nerds are still arguing about that one. Also about that time the Amazons invaded the US because they were torturing Wonder Woman as a terrorist. I’m not sure I count that one, though, because they copped out with “the bad guy orchestrated everything” eventually.
Seriously, I promise, comics are weird and have been going for a long time. Writers are gonna write all sorts of stuff. I know it’s reassuring to boil it down to archetypal stuff, but yeah, no, people have been messing with these characters for the better part of a century from every angle.