My impression of the readership is that it depends on the time of day. When I was in Vietnam, I would wake up to US centric posts full of comments. When I wake up early on the East Coast of the US (~6:30 am) I see more comments from Europe/UK. By mid afternoon, most of the posters seem to be from the US or at least the Americas.

I base this on about 5 years of daily HN reading. I infer the posters’ locations from spelling, grammar, but most often their own admission. Nonetheless, this is just anecdata.