The US can see Canada is dysfunctional and chose now to push on this, knowing if they waited for a new CPC government there would be far less dysfunction.
Canada ought to rethink it's relationship with all provinces. If one province continues to get privileged treatment while another degenerated, don't be surprised if things get shook up when a far better deal emerges. People can only be taken advantage of for so long. Canada wouldn't be harmed by the departure of Quebec from federation, but would certainly suffer if any of the western one's left. Fair treatment and progress on matters of national strategic importance (energy) is all it would take to improve unity.
If there are no fundamental shifts in this country and a good US deal remains on the table, if I were the Cdn Government I wouldn't want to chance putting it to a vote.