A unified North American trading powerhouse has long been seen as a potential bulwark against China. But Trump has repeatedly threatened to take over Canada and has targeted Mexico with some of his toughest tariffs. New Canadian Prime Minister Mark Carney has warned that his country’s traditional relationship with Washington is over.

President Donald Trump’s rapid-fire trade war has set in motion a commercial rupture without precedent, which is rippling through the global economy in unpredictable and costly ways. The triple-digit taxes that the president has imposed on Chinese products — and China’s retaliatory measures — are expected to shrink trade between the world’s two largest economies from a recent annual peak of nearly $700 billion to almost nothing.