Consent makes all the difference. Trump's talk of forcing Canada to become the 51st state via economic pressure stiffened the spines of Canadians and made it impossible for the Carney government to accept the same sort of deal other countries were getting. At the same time, it made closer relations with Europe look like a solution.

The reality is that the joining the EU as full members involves too great a sacrifice of sovereignty for middle powers like Canada, Australia, New Zealand, Japan, etc.. Brussels is too far away and the EU itself barely functions with the members it already has. There is, however, broad will among middle powers to work together more closely than they do now. This associate EU member thing needs to strike a balance where countries who join it can cooperate and contribute without feeling like the EU is becoming another U.S..