On that specific point no they don't go in depth, but then it's a short interview. He does say it's a comment on contemporary American culture, as with the rest of the movie you interpret it your own way. Clearly though from the interview he makes it clear the intent was political satire, and a deliberate critique of fascism and kind of world and people it might produce. That's the lens to look at these things through. But there is no one way to read it all, that's why I find it so re-watchable.
If you want to read it that all the other cultures were wiped out in the war and only one culture survived, sure.
If you think the one world government imposed a monoculture, maybe.
If you think humans are herd creatures that naturally converge on group-think consensus and globalisation is just going to go that way, fine.
Or maybe it was lazy film making cutting corners for budget and convenience reasons. OK. But in rebuttal to that possibility I submit in evidence the entire back catalogue of Paul Verhoeven movies.