If aliens were to visit only NYC for example, they would see people with widely different clothing, hairstyles, attitudes, walking the same streets. Even in 2506 (if we survive that long) I have great difficulty imagining that people in Jakarta and NYC would be impossible to tell apart (as they would be on all Planet of Hats ST monocultures).
I concur that a human monoculture is unlikely for a long time. Another question that I neglected to mention is whether extraterrestrials would perceive us as having a monoculture by their
They wouldn't be looking at out clothes, hair, or any of that. Those are little local regional subcultural differences. They'd look at how we conduct our lives and the operating forces behind them. Looking at it that way, we HAVE a global monoculture.
Every day, no matter where you live--NYC, Jakarta, Buenos Aires, Mogadishu, Nuuk, Astana--people live in exactly the same way
. They all get up, go to a designated job, toil hard and for long hours to get a symbol, take that symbol and exchange it for food. Everywhere. WITHOUT FAIL. The food is locked up everywhere, thus causing the control.
Oh, sure, there are people who refuse to live that way, but they're weird
. They're not us
. We've wiped out all but a tiny fraction of a percentage of them through disease, conquering, assimilation...but in some remote area, they still endure. And they have much to reteach us.