Besides everything else, today Superman is an almost satirically strict exemplar of what a "good" immigrant has to look like: if you can pass as a white able-bodied heterosexual male, were raised in a small Kansas farm, got a prestigious job in a traditional professional field, and save the world two or a hundred times, then you, too, might be accepted (or shot at on sight on account of what a scared cop or soldier thought you might conceivably do, that might happen too). But he was originally something far uncannier and politically disruptive.
Raised in an orphanage, he called himself not a crime-fighter or a world-saver, but a "champion of the oppressed." Wikipedia has a fascinating list of his feats in the much-coveted but seldom-read Action Comics #1 he
- violently breaks into the Governor's mansion in the middle of the night to deliver a confession to stop an execution
- throws around a man who was beating his wife
- rescues Lois Lane from a man who abducted her after she rejected him (the man's a gangster, but the car about to be thrown in the famous cover isn't "a gangster's car" but "the car of a man who was about to rape a woman who rejected him")
- "forcefully interrogates" a corrupt US Senator to obtain information about his crimes
That's not the national icon who gets a statue from the thankful government of Metropolis. That's the creation of a couple of Jewish immigrants and sons of Eastern-European immigrants in a US that wasn't necessarily welcoming of either group, people who knew first hand that what you needed wasn't protection from alien invasions, but from abusive men and corrupt politicians.
Going slightly back in time, the cultural roots of Superman lie not in Krypton but in the ghetto of Prague, where, in the classic telling of Judah Loew ben Bezalel's legend, the Rabbi created an invulnerable, super-strong, unstoppable golem — using, in a sense, the advanced technology of a long-dead world — to protect the inhabitants of the ghetto from the many forms of formal and informal violence they were subject to. The legend usually ends up badly in ways that would make Lex Luthor nod in approval, but, long before rich and privileged Victor Frankenstein successfully created life and completely flunked his ethical responsibilities about and towards it, there was already a tradition of non-/super-human life created by the knowledgeable oppressed for specifically ethical and political goals of communal survival. The focus of Superman as immigrant, his tale of his assimilation into and to America, is a relatively later development, as is his deployment as a sort of long-surrendered ideal of what American "hard power" should and should *not* do.
He was to begin with created by and for oppressed groups, using the then-new idioms of science-fiction to retell the story of a supernatural equalizer called forth when the all-too-natural mechanisms of society are overly stacked against you.
There's no need to remark that all of the crimes Superman fought in Action Comics #1 were and are real and frequent. What might be worth pointing out is that, although our contemporary zeitgeist is one in which the uncanny is becoming increasingly operational and under the control of established powers — where billionaires plan Mars bases, cops in authoritarian countries have cybernetic access to facial recognition databases, and ubiquitously surveilled smart cities are prototyped by companies that are also vying for military contracts for targeting image analysis in, one dreams of being able to hope, completely unrelated developments — there's an older thread of ideas just below the surface, one in which radical technologies aren't just deployed by the powerful, but also as forms of both individual and communal resistance.
Captain America is less a metaphor than an entire category of military R&D grants, and more than one billionaire thinks themselves Tony Stark. But, in the inertia and apparent closure of our current narrative about our increasingly weirding, pre-/would-be posthuman future, let's not forget that the radical application of new technologies can also take place in the political margins. There's agency there, too, and new potential futures, all built with the age-old goals of community and survival, even if using new and stranger clay.