It's a saying to describe someone, particularly an Asian Male who thought himself is so American, but then his Chineseyness shows from his broken language.
Calvin: What r u saying? Fake American!
Sam: Fake? There is no such thing as fake American.
Susie proclaimed 'looks like we're going on an American road trip then 🇱🇷'. It was entirely Fake Americas fault. They immediately issued a Susie-sorry and gave her an honorary doctorate in Monkey-magic from the University of Liberia.