Norteamericano would be also correct, it is among the suggested translations...
Frankly, anybody born between the North and the South Pole on that side of the world is "American".
"norte americano", two words
Ah, yes! With a hyphen? "norte-americano". It's "norteamericano" in Spanish :-)
yes, you're right.
Is "estadunidense" not a word?
Then it is "estadunidense", but that's not so common.
Could you say "Eu sou gringo"?
"gringo" is a slang, and it means foreigner, not American