On the evening of June 18, Los Angeles will briefly become two cities. Koreatown erupts in red at Seoul International Park for Korea vs. Mexico. At LA Plaza de Cultura y Artes -- the Government of Mexico's official cultural home for the World Cup -- the courtyard fills in green as el Tri fans watch the same match from the other side. Both communities, watching the same game, across town from each other. Casa Mexico is the Mexican American answer: an official government-designated gathering space where this match is not a sports event but a cultural moment. The outdoor screens go up, the food vendors set up before the 6 …