If tariffs evolve from a negotiating tactic to a new normal, economic and diplomatic costs to all of North America will grow.

U.S. President Donald Trump's tariffs on Canada and Mexico kicked in at midnight, triggering a North American trade war.

U.S. President Donald Trump says his long-threatened trade war is going ahead with tariffs on Canadian goods set to take effect just after midnight and there's nothing Canada can do to stop them.Speaking to reporters at the White House,

President Donald Trump's decision to impose blanket tariffs on Canadian imports — which went into effect Tuesday — and his increasingly hostile rhetoric toward the U.S.'s northern neighbor have deeply strained the relationship between the two countries.