Fighting TrumpSeems to me that Canada needs to take a chapter out Pierre Trudeau's book when dealing with US threats to limit exports from Canada to the US. One of things he proposed at the time and one which caused the US to back off was to threaten to impose an export tax on oil exports to the US.
Since the Gulf Coast refineries are heavily dependent on Canadian oil for feedstock, this caused a sober second thought on limiting Canadian exports and imposing tarrifs on Canadian resource exports to the US. In addition Trudeau threatened to turn off the taps for Canadian exports of water to the US and this caused the farmers in the Midwest to push for a change in US policy (don't forget that not a drop of the water from the Colorado River actually gets to the ocean)
In today's world such a policy decision on oil exports from Canada would cause fuel shortages in the US and a massive spike in inflation. Something that would sink Trump's popularity real quick.
IMO Premier Ford has taken this lesson to heart with his threats to limit Ontario electricity exports to the US.