@maxdancona,
It's interesting how you you seek to Resnais facts to fit your point of view.
While the sense of unity did, alas, fade with time, it certainly lasted a lot longer than two or three days.
Depending your use of the word "nationality," you could be very right or very wrong. I think I understand your usage and you are very wrong.
Many people in America or at least it's regions of heavy immigration (ie NYC where I grew up) refer to someone's heritage when they speak of their
"nationality."
A New Yorker's "nationality" consists of the countries from which his or her forefathers emigrated. It's not..."American"
In this context,
nationality was, indeed, meaningless in NYC on 9/11, because the overwhelmingly prevailing sense of identity was American, or New Yorker. It certainly wasn't World Citizen.
Your perspective seems to be that as individuals we should align our sense of identity to the greatest set of humanity: Earthlings. I would find it more intriguing and coherent if I thought you advocated the opposite: aligning ourselves to the base sub-set of humanity: Individual Self.
What happens when proof of non-Terran life arises? If you're alive, will you find "globalists" to be repugnant?
Human Nature has developed because it favors the survival of our species, and personal associations are a big part of Human Nature: Family, Tribe, Clan, Nation...
You can find this problematic, but I don't. Generally I concede that while self-organizing systems may not have any "intelligence" and so are not more intelligent than me, they are better suited to determine broad outcomes than me.
I bet you do too:
Should mankind try and manipulate ecologies?