Donald Trump appeals to Republican voters by repeating his promise to build a "big, beautiful" wall on the US-Mexico border. But it turns out that the border already is more secure than ever. More Mexican immigrants are leaving the US to return home than the other way around. And increased security is producing unintended consequences — for a massive trade relationship and for people who live and work on both sides of the border. We hear how it looks now to those cross-border neighbors, including the many new agents of an expanded border patrol.