Then I gave examples where certain characters, based on their back-stories, necessarily need to be certain races. You largely dismissed those out of ignorance.
No, you missed the point completely. You seem to have no problem with Johnny's backstory changing from blood relative of Sue Storm to an adopted sibling or sibling-in-law. Yet you cannot tolerate a world where several other characters could undergo a similar change in back story. Natasha could be a while American or a Japanese spy or a black chick from Russia. If you're willing to accept the change for Johnny, I see no difference in a change of origin for others. Hell, is the movie version of black widow even Russian? She sure doesn't seem it. And yep I read the Punisher comic for years. He is Italian, but they could rewrite that into a poor Hispanic immigrant who loses his family as well - maybe in a gangland shoot out in the South.
Now try these on for size. The Black Panther is a black superhero from Africa, heir to the throne of Wakanda. What if they cast Panther as a white guy from South Africa instead? There are plenty of whites there, so no big deal, right? What if they made a Luke Cage movie about a poor white guy from New York who goes to prison, then redeems himself after an experimental procedure gives him steel-hard skin? Falcon, Storm, War Machine - any issues with those characters being played by white guys?