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
Well there's Star Trek and the way they choose to represent the universe and then there's real life. My opinion of real life is that I find it very difficult to believe we could communicate with intelligent life-forms who had not evolved (and therefore shared with us none of our evolutionary characteristics), since that would mean they would exist in a way that is almost impossible for us to imagine. Of course, I may be proved wrong in 3069.
Well, the problems of humans being unable to recognize aliens ("The Devil in the Dark" and "Home Soil") and of aliens being unable to recognize people (The Motion Picture
) have both been treated in Star Trek.
Having difficulty communicating with aliens has also been treated ("Darmok").
I think that we shouldn't be surprised if real extraterrestrials end up being far more alien than we're accustomed to seeing in science fiction films and TV. With no examples to point to, I think it's not inconceivable that we might have trouble establishing a common frame of reference, even with aliens who evolved in their habitats similarly to how we evolved in ours.
What I'm getting at is that the problem of aliens existing in ways that we can't even imagine might well extend to aliens who evolved also.
Even for aliens who we could recognize, and who could recognize us, communication could be practically impossible for cultural or even instinctual reasons. For example, if they were predisposed to regard us something that they must
eradicate, it might be impossible to carry on conversations with them of any kind, even though their science might be based on principles similar to ours and even though we could recognize each other.