Complex sentence: One such resident was the comic film actor Germán Valdés, a native of Mexico City who grew up in Ciudad Juárez (just across the US-Mexico border from El Paso), whose films did much to popularize the language in Mexico and the United States.
Split into simpler sentences: One such resident was the comic film actor Germán Valdés, a native of Mexico City who grew up in Ciudad Juárez (just across the US-Mexico border from El Paso). His films did much to popularize the language in Mexico and the United States.