Matthew Lynn is a financial columnist and author. He writes for the Daily Telegraph and the Spectator in London.The White House ballroom? Appointing Elon Musk to streamline the federal government? A war against Iran? When future historians try to work out what was the biggest flop of President Donald Trump’s second term, they certainly won’t be short of choices. But the winner is surely already clear: the “gold card” visa. It has turned into what the president would usually refer to as a “total loser.” And yet, it wasn’t a terrible idea. Perhaps the White House should try again?