An Afghan national with ties to the Taliban — and a plot to carry out a terror attack somewhere in North America — was caught last fall after being smuggled into the U.S. from Mexico, an incident sure to further inflame the debate over national security risks at the border. The Afghan national’s alleged terror ties were not initially flagged in a terror database – and as a result, not initially reported – when the incident first came to light last November, according to Rep. Duncan Hunter, R-Calif., who obtained Homeland Security documents on the incident. It was only later...