At a moment when the familiar architecture of North American trade is under strain, Canadian Finance Minister Mark Carney is traveling to Europe with a proposal that would rewrite the rules of transatlantic partnership. Facing an increasingly unpredictable relationship with Washington, Canada is seeking something unprecedented: associate membership in the European Union, a status that has never been extended to a nation outside the EU's traditional orbit. That EU Commission President von der Leyen reversed her decision and chose to attend Carney's speech suggests this is not diplomatic theater