The more egalitarian principle would be to not assume. I won’t deny that. People from more minority locales have every right to be upset at being marginalized.

But at the same time, whenever I read passive aggressive comments on socials from crown countries or from EAASL people around the world bitching about US defaultism as if people are doing it just to be ignorant dicks, I can only think to myself, “Uhh, hello? What do you think the demographics of this space were? What did you expect?”

Americans are hardly the majority of the world’s English apeakers, but for all the reasons you listed, they tend to remain a massive plurality, if not an outright overwhelming majority, of any mainstream online English language platform. No, that’s not a license to perpetuate US defaultism. But like… read the room, people. Your good fight is far more uphill than you seem to think it is.