At the end of the day the United States can do what it wants.  You would also be a fool to thing it will not hurt.  It will hurt really bad in certain sectors.  We won't lose it all, and the same applies to the USA.  Certain parts of Canada will hurt more, some less, but we will collectively feel the pain.  It is possible to end it in court or not.   Of course having priority access to Canadian oil is a premium.  Think about it, second largest reserves in the world, right next door.  A deal that allows access to it!   Consider the significant expeditures, try to keep the ME stable and what would happen to oil delivery if war starts.  It is like America has an army gaurding a massive oil reserve in Canada, at no cost....just a trade agreement.   Sure as usual Quebec and to a lessor degree Ontario can make cheese.  Sure BC gets to cut down tree on public lands ( I think).  So what compared to trillion spent on defence, linked to oil.