[devilbunny]

This is one of those places where in some languages - Spanish, of course, and I would assume Portuguese - "americano" (or equivalent) basically means "Western Hemisphere". But in others, like English, "America" means the United States of America, just like "Mexico" means the United Mexican States. If you're using English, "North American", "Central American", and "South American" cover most of the situations you're talking about. "American" without further qualification in English means the USA. And it is justifiable: there is exactly one country on the planet with "America" in its name.