1 MONTERREY, Mexico — There is a scene near the end of the film “I’m No Longer Here” (“Ya no estoy aquí") in which the lead character, a stoic Mexican teenager named Ulises, walks along a highway in New York City, huffing paint thinner. Forced to flee his country after a misunderstanding with a gang, Ulises has been crushed by the isolation of immigrant life and is ready to give up. For Juan Daniel García Treviño, who was a 16-year-old construction worker with no acting experience when he was cast as Ulises, it was the most difficult scene to film because it recalled his own harrowing adolescence in a notoriously rough region of northern Mexico.