The young Chinese man looked lost and exhausted when Border Patrol agents left him at a transit station. Deng Guangsen, 28, had spent the last two months traveling to San Diego from the southern Chinese province of Guangdong, through seven countries on plane, bus and foot, including traversing Panama's dangerous Darién Gap jungle. "I feel nothing," Deng said in the San Diego parking lot, insisting on using the broken English he learned from the "Harry Potter" film series. "I have no brother, no sister. I have nobody." Deng is part of a major influx of Chinese migration to the United...