In the long and tangled history of neighboring economies learning to live with one another, the United States and Canada have arrived at a moment of deliberate rupture. President Trump's ultimatum to Bombardier — build on American soil or lose American customers — is less a trade policy than a philosophical declaration: that access to the world's largest consumer market must now be earned through physical presence, not merely commercial exchange. The threat lands amid a cascade of retaliatory tariffs rooted in a disagreement over how to confront China, revealing how swiftly a single geopolitic