The US may have been a somewhat reliable trading partner until recently.
Remember that Trump ran on protectionism and was elected on protectionism. In other worse, he is in,fact acting on his mandate. This means too that Trump is less of a problem than his voter base. It's also nit a right or left issue. We could gave run into a similar problem with Sanders. Between Trump and Sanders, the US today has a large protectionist base and it won't likely just disaappear because we get rid if Trump.
The USA of today is not the USA if the past. It's still an important trading partner for us, but it is also debt-gießen and no longer represents the sane fraction of the world's wealth or GWP as it used to. Untethering ourselves from the US and unilaterally dropping all trade barriers would be painful at first, but it would also name us more resistant to growing US protectionism later on.
The US is not as reliable and predictable as it used to be and wants to close in on itself.
We could always start gruadually. For example, declare Montreal, Toronto, Vancouver, and Halifax Free Economic Zones and start from there. Once they'll face adapted, then add more municipatities and provinces until Canada becomes a Free Economic Zone.