Well I am from the US. When I am asked what is my nationality by someone I answer "Irish and English" as that is where my maternal and paternal families originate. Only term I have heard re: US is American as in "Ugly American" or "Americans go home" or "I really like American Jazz".

I agree that Canadians are also Americans as are the folks from central and south America as well.

I didn't coin the nomenclature so it isn't my fault, honestly. Someone else did it. I guess they did it cuz United Statesian sounds so silly. Of course if one were to add a silly walk with that nationality we would have to include you brits in there too somehow as you've got the ministy of silly walks over there.