cancelling oil exports - or mineral exports - to the united states would eliminate a tremendous amount of wealth in canada. making ourselves poorer seems like a dumb way to stick it to the man.
it's a better environmental argument to leave it n the ground, and arguably worth supporting on that basis, than it is an economic argument to shoot ourselves in the face. it is abundantly clear that it will not change american behaviour, it will just destroy wealth in canada.
it makes more sense to try to recover losses by levying export taxes on americans. retaliatory import taxes and export blocking are both dumb tactics.