America's path to lower inflation depends in part on trade wars and actual wars becoming less economically disruptive. In recent days, both have taken turns that threaten the opposite. Why it matters: A period of relative calm on those fronts is now giving way to renewed tensions, with Canada, China and Iran all posing fresh economic risks. What's going on : The U.S.-Canada trade fight is shaping up to become an all-out trade war, threatening economic and political fallout on both sides of the b