The BBC ran an amusing story about The American Mistake about the new baby. They're saying that when American news presenters call the baby "the future King of England," they are wrong because the country is not England, but the United Kingdom, which includes Scotland, Wales and Northern Ireland.
Well, BBC, this isn't a mistake, though I'm sure few American media people realize the kid isn't a future "King of England." What is is, is a convention, or tradition. It's like saying, "Washington is going to regulate cigarette smoking." Laws "from Washington" are not actually coming from the city called Washington, D.C. It means the federal legislature and the Office of the President.
Of course, the BBC couldn't let "The American Mistake" pass without taking the opportunity to preach about tolerance. They made a good comparison to calling the United States "America", which isn't technically accurate.
- So can we legitimately use "American" as an adjective referring to something from the US? If so, you're back in the Britain/British quagmire again. Perhaps the answer is for everyone to be tolerant, to embrace a bit of "constructive ambiguity"... and just toast the health of the future king.