Why the situation on America’s southern border has become unmanageable

THE SITE has an air of abandonment, like a half-finished apartment building whose developer ran out of money. Thirty-foot (nine-metre) steel rods rise from the desert sand. The area has been electrified and prepared for floodlights, but only half a dozen have been installed, so most of the structure is bathed in darkness at night. Thanks to Donald Trump the border wall, of which this is part, has become a charged symbol of nativism and exclusion. But the design of this stretch, with slats spaced four inches apart to let people see through, is similar to the 128 miles of wall built during Barack Obama’s presidency, just taller. It was built hastily during the final months of Mr Trump’s term. Strewn nearby are steel piles of the old, shorter wall, which have yet to be hauled away.