It was a claim that President Donald Trump repeated on the campaign trail: that he would build a wall and that the Mexicans would pay for it. In his first few days in office, Trump appeared to make good on one portion of that promise, by signing an executive order for the planning and building of that wall to proceed. But the cost for that wall will temporarily be borne by Americans, Trump said, and Mexico’s government insists it will not pay for the construction on the border. On Thursday, President Donald Trump floated a 20 percent tax on imports...