The 2006 film Quinceañera premiered in the United States before its theatrical release.
The film debuted at the Sundance Film Festival in Utah, an American festival known for showcasing independent cinema. It was directed by Richard Glatzer and Wash Westmoreland and tells the story of Magdalena, a teenager in Los Angeles whose pregnancy affects her family and her planned quinceañera.
Its Sundance success helped establish the film internationally. Quinceañera won both the Grand Jury Prize and the Audience Award in the dramatic competition, then reached wider audiences through distribution. The movie’s setting is specifically Mexican American Los Angeles, which can lead viewers to assume that its premiere occurred in Mexico.
A premiere refers to a film’s first public screening, not necessarily the country where its story takes place or where its cultural traditions originate. That distinction makes the question different from asking where the fictional events happen.