MISSION — U.S. Sen. John Cornyn said Tuesday that building a fence along the southwest border is unrealistic and ultimately would not deter illegal immigration into the United States. Cornyn, R-Texas, was in Mission on Tuesday to discuss flood control and the Rio Grande Valley levee system, but spoke briefly with the media about immigration issues and his plan to allow workers into the country legally but temporarily. He said he would not support a bill calling for a security fence — which could start in California and end in Brownsville — although the U.S. House of Representatives approved the...