I have to side with the Americans on this, that Canada, as a country that depends greatly on trade, depends on passage between other straits in the world. Our shipment of oil—if we want to ship it elsewhere—is going to pass through straits that belong to other countries. By the law of the sea, as I understand it—I'm not any legal expert by any stretch—basically Canada is pretty close to being alone in interpreting the Northwest Passage the way it's interpreting it. I think the best interest of Canada in the long run is to trade, essentially, and compromise with the United States over the Northwest Passage, and perhaps get a better slice of disputed territories beyond where Alaska and Canada meet offshore, where there are controversies over where the territory is.
Thus, I think in the long run it's not going to be beneficial to Canada to have a fight of Canada versus the rest of the world on a point of international law that Canada has agreed with up until this point in time, until it became inconvenient up north with the melting of the ice cap.