The majority of Facebook users access it from outside the US.

That doesn’t preclude them from using it as one factor in their abuse detection models.

Whether it’s a good idea or not, geolocation is a common factor that these models take into account.

I think it's good to add to the discussion here for other HN readers that the reason I mentioned it was that some people are suggesting this is a measure put in-place by facebook to reduce election interference (as it's happening right now in the US). That may be the case, it may also not be since everyone (doesn't matter where from) seems to be getting banned alike.