Translation:A German visits an American in the United States.
To me, using a demonym for someone that's from the US that's other than "American" doesn't quite make sense. It would be like calling someone from the United Arab Emirates a "United Arabian" instead of an "Emirian". Officially, Mexico is the United Mexican States but we just call them "Mexicans". When I read a name like the United States of America, I read it as, this country is made up of many little states to form one big country that's in America. To say someone is a "United Statesian" would be like saying someone is a "Republican" when referring to someone who's from France, officially the French Republic. Just because the US's name just so happens to have the name of the continent it's in doesn't mean it owns the entire continent "manifest destiny-style", read it as: these United States that are from America. Finally, if people are so caught up on countries and continents, think of this: when calling someone an "Australian", are you referring to the country of Australia or the continent of Australia?
This is coming from someone that's non-American (as in, not an Usonian).