Chrissy, that's funny that you mention that, because I have tried to use that argument time and time again with British friends and friends of other nationalities that I am not just "American" but that I'm from the USA and that "America" includes more places than just the US, and I always get a puzzled look and then an arguement back, yeah but you're an American, people from the states are American and people from Canada are Candian and people from Argentia and Argentian, etc. But like for instance, I remember when I had my national insurance interview the lady put on the form for my nationality, "American"
Okay, whatever! I don't even know what to call myself, because saying you're USA'n is bizzare, so for simplicities sake I've said usually I'm from the "states"-
But anyways, on immigration forms, I usually put USA or United States of America, depending on what fits...