...legally, I am an American.
That's what these cats don't understand. Jurisdiction.
Any time anyone, or any jurisdiction wants to classify me as something other than American, it is because they want something. Something of which I have neither a need for, nor obligation to fulfill (outside of the threat of punishment for something I am not guilty of).
What is an "American"? Italian explorer Amerigo Vespucci is who the "Americas", a continental land mass, was named for. Ergo, "Americans", technically, includes, but not limited to, Argentinians, Brazilians, Mexicans, Canadians...etc, just like "Africans" include countries from south, central and northern parts of the continent. Its "The United States" of [the] Americas.