In a lot of different languages, the word for people from the USA is the equivalent of "Unitedstatesians." People grow up with that, and I can see how it would be a surprise to visit the USA and realize that the people there nickname themselves in such general terms as "Americans" without being specific as to which kind of Americans they are.
Still though, hard to figure out a better solution, and this is only the tip of the iceburg. It would be correct to call someone from the UK "British" if they came from England, Scotland or Wales because that is Great Britain. But what if they were a UK citizen from Northern Ireland, which is not within "Great Britain?" Well, thankfully it is all still the British Isles, so British still applies. But then again, it applies to the Republic of Ireland for the same reason. Not too sure how many Irish citizens appreciate being called "British" however. HAH.
While we're at it, quit calling it Holland when you mean the Netherlands. That would be like calling someone a Californian when they're from Ohio and you meant to call them an American...ummm...I mean a Unitedstatesian. Oh wait...sorry to Mexico which is also made up of States... A Unitedstatesofamerican???
I'd call them Yanks, which we do in Canuckland, but apparently this doesn't apply to southerners. Don't even get me started on Canada. Newfoundland had a perfectly good name, but the province next door is grabby about their land, so just to rub it in, they changed the name of their province to Newfoundland and Labrador. So what are they now, Newfoundlandandlabradorish? Newfoundlanders was so much easier. Then up north, they created a new territory, Nunavut. Which means "our land." Hardly very specific is it? So now we might say "Allow me to introduce Peter. He's from Nunavut. Well, actually he's from their navut, not our navut. The really cold navut up north of Quebec."
I'd just be happy if the Americans (sorry, I mean the Unitedstatesians) would make up their minds on the news as to whether it is "eye rack" or "eee rack" or "eye rock" or "eee ruck."
The British also need to decide if it is Packistan or Pockistan or Packiston. I'm sure I've heard all three, presumably as different newscasters vie to sound more British than each other. Errrr. I mean more "Britainandnorthernirish."