TIJUANA, Mexico—In a dim church auditorium with three-story ceilings, nestled at the bottom of a steep, trash-strewn canyon in Tijuana, Mexico, the loud cries of hundreds of children pierce the air. Huddled inside, some sleeping on mats, over a thousand migrants from Central and South America have sought shelter in the Iglesia Embajadores de Jesús, one of the only indoor options they have while waiting to navigate the path to U.S. citizenship. Thousands of travelers have flocked to this border town, lured by the promise of newly elected U.S. President Joe Biden and a loosening of immigration restrictions, hoping to escape oppressive conditions in their homelands and start a new life in America. But for many, this is as far as they will get. According to U.S. Customs and Border Protection figures, over 172,000 people were taken into custody in March alone. Over 53,000 of them were family groups, and …