Como se dice "gringo" en espanol?
True, they are all Americans, but even among Hispanics, the terms "norteamericanos" and even
"estadosunidenses" are just to cumbersome to use in ordinary conversation. Even the latter is problematic, because there is a United States of Mexico and a United States of Brazil. So the term "Americanos" is usually employed.
Personally, I prefer the term "Yanqui", but lately it's picked up negative connotations. Probably because of the baseball team of that name.