Two nations whose economies have long been stitched together by a trillion-dollar web of commerce now find themselves pulling at opposite threads. Canada, responding to American tariffs with retaliatory measures of its own, is forcing a reckoning with how much prosperity has quietly depended on the assumption of goodwill between neighbors. The dispute is not merely a policy disagreement — it is a stress test of an interdependence so deep that its unraveling will be felt not in headlines alone, but in the quieter ledgers of factories, freight yards, and family paychecks.