President-elect Donald Trump won’t be sworn into office for another seven weeks, but he is already possibly destabilizing international relations and domestic markets by constantly threatening to impose new tariffs. In just the past month alone, he has threatened to impose a 10% tariff on all imports from China, a 25% tariff on all imports from Canada and Mexico, and a 100% tariff on all nine of the BRICS nations: Brazil, Russia, India, China, South Africa, Egypt,...