So far, American consumers have been shielded from much of the impact. But as the world of international shipping adjusts to his policies, the president is facing a potential reckoning. With the US-China trade war starting to gum up container traffic between the world’s two biggest economies, freight companies are warning of plunging bookings and a surge in “blank sailings” – where ports are skipped or voyages are called off altogether. Earlier this week, America’s most powerful retail executives trooped into the White House to deliver a blunt prognosis: tariffs on Chinese goods risked causing “empty shelves” in two weeks...