Why is Trump threatening Canada with new 50% tariffs?

The U.S. trade war with Canada escalated on Monday when President Donald Trump announced that his administration would be imposing new 50 per cent tariffs on a wide range of Canadian exports in 30 days' time. Washington correspondents Willy Lowry, Katie Simpson and guest host Mike Crawley explain everything we know about these new tariffs and ask what they mean for the strained U.S.-Canada relationship.