President Donald Trump threatened to double tariffs on Canadian cars on Monday, the latest sign that the United States and Canada are barreling toward a deeper trade war after last-ditch efforts to strike a deal collapsed Friday.

Canadian Prime Minister Mark Carney vows to retaliate, says his country recognized that 'America has changed' and that the two countries would 'not return to our old relationship'

United States President Donald Trump imposed fifty percent tariffs on Canadian imports. Canada's Prime Minister Mark Carney promised matching retaliatory measures starting…