In Brazil we use "americano" (it is Portuguese noun too) to refer to someone that was actually born in the USA.
I recall when I was a kid at school that a teacher once said even though we don't regard our selves as americans, it wouldn't be wrong to do so since we are born in south america. Then she'd say that we should refer to people born in the USA as "estadunidenses", but no one here does that, and if you do people will find it funny.
I recall when I was a kid at school that a teacher once said even though we don't regard our selves as americans, it wouldn't be wrong to do so since we are born in south america. Then she'd say that we should refer to people born in the USA as "estadunidenses", but no one here does that, and if you do people will find it funny.