Trump unilaterally decided to levy a 25-percent tariff on our long-term ally, Canada, which exports a variety of products to many states in the U.S., including electricity and crude oil. The key states for receiving electricity are Minnesota, Michigan, and New York. Canada transmits 27 million megawatts a year to the U.S., serving 1.5 million homes in these three states.  It has 31 transmission lines crossing the U.S. and Canadian border and provides smaller amounts of electricity to other states.
If Trump pursues an onerous tariff tax war on Canada, Canada might consider its own 25 percent tax on electricity exported to the United States or if Canada becomes really unhappy with Trump’s actions, it might flip the switches on the border transmission lines to “off.”  Blackouts would affect over 1.5 million homes, including larger cities like Buffalo.  In cities, blackouts would impact restaurants, stores, hospitals, factories, churches, and shut down charging stations for electric cars.  Prices on American homes and other real estate will crater at the prospects or reality of Trump’s Canadian tariffs tax war.  
An additional consideration is that Canada is a major supplier (285 million barrels a year) of heavy crude oil to the U.S. oil refineries.  Refineries are very expensive and take a long time to build or retrofit. If the Canadians decide to sell their crude oil elsewhere, (and there is a pipeline already under construction to their West Coast ports), the U.S. will have to pay more to import heavy crude from long distances, if it’s even possible, for replacement.  “Drill baby, Drill” oil cannot be used as a replacement because most of the oil drilled in the U.S. is light crude.  
Gerry Snyder
Ely