Abel Oset was seized with panic. The two were going to plead their case in a court set up inside a tent in Laredo, Texas, beamed via video conference to a judge in another city — the latest attempt to clear a massive backlog of asylum cases. Oset dreaded the very real possibility that he and his 22-year-old son would be sent back over the international bridge, back to Nuevo Laredo, in Tamaulipas, and its cartels and violence.