I see opportunity not collapse. Let America close it doors. Every market they withdraw from is one Canada can move in to without having to hand the tastiest bits to the USA. 
It is absolute hog wash that America has been making win-win deals for the last 70 years. Every trade deal the US makes has been weighted in the favor of American Finance Capital.  The Marshall Plan prevented a return to the pre war economic recession in America where war time industrial capacity would suddenly have been unneeded had Europe been unable to rebuild. The rare exceptions were during the cold war when concessions were made to the likes of Saddam to prevent the spread of communism.
I am most concerned with the possibility that Trump will try to recreate post world war II prosperity with another war. Which is also effective in getting rid of a many thousands of angry unemployed young men and women.