Negotiations between the neighboring countries broke down Friday in Washington, putting into force new 50-percent US tariffs impacting about $20 billion worth of goods, or 5.5 percent of Canadian exports to the United States.

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…