Pitiyanqui = Petit yanqui (in french) = little yanqui WHERE yanqui = US citizen
This word is despectively about people from other countries that live like Americans ("Americans" in US sense). I want to be clear on it: US people is not the problem but guys believing thenselves "Americans" (US citizens) while they are living (and to be from) other countries. People make a fun of them. I don't know "properly way" of saying it: people see them like... feet-lickers? Sorry for my language barrier.
I don't think people in the US have ever heard the term, so we probably don't know exactly what type of behavior it refers to.