“This is cultural bias in effect. General (generally white) audiences never question why characters are white and blond. If a character could be white, that’s usually justification enough. Whiteness as default becomes logical and comfortable. Only non-whiteness requires an explanation.
Indeed, if a character is not white, some people will cry out that their racial identity is the product of political agenda-driven tampering. If a character is white, the same people will comfortably assume that he or she came out of the box like that.
It should be noted that we’re not even talking about the broad US census category of “white”, which covers people whose families hail from Europe, North Africa or the Middle East — including many people with tan, olive or ruddy skin.
In comics, whiteness is predominantly represented by the pale pink complexions of Northern Europeans — the color once problematically referred to as “Flesh” on Crayola crayons, until Crayola changed it to “Peach” in 1962. Real world white comes in many shades, but in comics all white people seem to trend towards hex color #FFCFAB. (Individual colorists may of course bring more nuance to their work, but how many white superheroes can you name who are consistently portrayed with bronze or olive-toned skin?)
Superhero comics don’t actually favor whiteness; they favor a subset of whiteness that borders on Aryan idealism. We ought to regard that as uncomfortably fetishistic, because it’s an aesthetic that the industry has chosen.
All fiction is manufactured. Authors make their worlds and choose what goes in them. It is always possible to contrive a fictional justification for a character looking whichever way the author wants, up to and including finding a way to make a white person the hero in a story about, say, feudal Japan, or ancient Egypt, or Persia during the Islamic Golden Age. A white hero is not the most likely scenario, but it’s always a possible scenario, so in that way it always becomes justified.
The decision to cast Michael B. Jordan as the Human Torch has been called out by message board posters as evidence of an agenda at work — but white heroes in these non-white settings are rarely called out as similar evidence of an agenda. It’s all artifice, it’s all contrived. Fiction exists in service to an author’s design. All fiction serves an agenda, whether it’s articulated or not.”