Final answer:
John Reed was the only American journalist to report from behind enemy lines in Mexico during the revolution.
Step-by-step explanation:
In the context of US-Mexico relations, the only American journalist to report from behind enemy lines in Mexico was John Reed. Reed was a journalist and a socialist who went to Mexico during the revolution in 1913. He reported on the events and interviewed notable figures such as Pancho Villa and Emiliano Zapata. His book 'Insurgent Mexico' is a firsthand account of the revolutionary movement in Mexico.