US president’s comments come after United States imposes 50% tariffs on $20bn worth of Canadian goods

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'

The United States is imposing 50% tariffs on $20 billion worth of Canadian products after last-ditch negotiations failed to resolve the latest strain in already tense relations…