Simple solution. 

It has long been the truth that the federal government cuts international trade deals to the extent it is easier for Saskatchewan to trade with Denmark, than it is for the province to trade with say Ontario. (depending on the product or service).

I suggest each and every province up its' connectivity with the neighbouring USA, and build trade that way.

I have long suggested that oil/gas pipelines from Alberta should reach the Pacific via the USA.

That will of course do wonders for building "national unity", and lower Canada's (assuming anyone cares about "Canada". Based on the present situation, the answer is most decidedly no) dependence on the USA, right?

And if you are laughing at that, tell me why that is not easier than trying to trade across provincial lines?