Thanks for the info, I'm American and haven't heard that term. Honestly, it seems dismissive to call a group of people something they don't call themselves.I've heard and seen plenty of people from the US use the term--I have.
Then you're literally the first I'm aware of. Seriously. And how do you even say it? "ooh-sians"? "Ewe-Ess-ians"? "Uhs-ians"? Or is it one of those things that only appears in text? And why do I never see "UKians"? Or "SAians" for South Africans? Given that, after all, there's more than just South Africa in south Africa.
It just boggles, is all.
I've seen both SAians and UKians before (granted, only seen the latter once or twice), on Twitter, mainly and usually in relationship
to either rugby or cricket.
I don't think I've ever come across anyone actually saying any of them, though - my experience is that all three are shorthands for textual mediums where you may have some sort of character limit.