So you are pretty confident that these days the humans are at their best when it comes to understanding things.
Hell no, that's besides the point. Humans have understood things better as tech advances, thus enabling us to learn things we otherwise couldn't, and theories are created and built upon. With that said, I am fully confident that us humans understand things FAR, FAR better than we did when the flat-earth model was widely accepted. Maybe in a hundred years, if we make it that far, we'll look back at allergies and think, "Wow, we're stupid for not eliminating those back then. Now I can frolick in the fields of Tennessee without wanting to fill my sinuses with cement!"
Are we at our "best?" I'd like to think we aren't. I hope not; it would be lame if humanity stopped short of ushering itself into some sci-fi type shit.
As for donut-earth, we have the tech and physics to figure that one out pretty easily, but, of course, everything's a conspiracy and NASA is lying to us, as usual.
That covers conversations I have as well, and I use that term jokingly and sorta sincerely (when appropriate, in context). If there was a better collective term it would probably be difficult to convince people to switch over. A friend one recommended USAians or something. Perhaps referring to the state/commonwealth/etc. will be better, as everyone will probably understand things like New Mexican and Georgian without confusion.
Speaking for myself, I wouldn't abide. Outside of the Easy, I have no love for Louisiana. If I move to a different state, do I just suddenly become Alaskan or Idahoan or Floridian?
Speaking in general, this country is polarized enough without people identifying more with their small corner than being proud of their country as a whole. Besides, the Old World sees people from USA as Americans and people from Canada as Canadian an Mexico as Mexican (at least when Central Americans aren't being shuffled into the same category), so on so forth. I say you can't please everyone and just keep it as it is.