PHOENIX -- Reyna Montoya was 10 when she and her family fled violence in Tijuana and illegally immigrated to the U.S. Growing up in Arizona, she worried even a minor traffic violation could lead to her deportation. She didn't feel relief until 11 years later in 2012, when she received a letter confirming she had been accepted to a new program for immigrants who came to the country illegally as children. “All of the sudden, all these possibilities opened up,” Montoya said, fighting back tears. The Obama-era Deferred Action for Childhood Arrivals program granted her and hundreds of thousands of...