When trade negotiations between the United States and Canada fell apart this month, the casualty list was longer than most people expected. Alongside steel, dairy products, and farm equipment, one unlikely item emerged as a symbol of economic entanglement: toilet paper. The US consumes more than 20% of the world's tissue products despite holding just 4% of its population, and much of the raw material comes from Canada's vast forests. The tariff dispute, it turned out, was always going to be personal.

The breakdown arrived despite signals from President Donald Trump that a deal was close. According to Canadian officials, American negotiators introduced unreasonable last-minute conditions that made agreement impossible, and US tariffs on a range of Canadian exports — from hockey sticks to tongue depressors — duly took effect. Prime Minister Mark Carney, who has positioned himself as one of the few world leaders willing to confront Trump directly, responded by announcing retaliatory measures on approximately $20bn worth of American goods. He described his country as having been "attacked", a word chosen with evident care.

Trump's reaction was characteristically theatrical. He threatened to rename Lake Ontario — shared by the Canadian province and the state of New York — "Lake America", dismissed Canadian negotiators as "clowns", and compared Ontario Premier Doug Ford unfavourably to unnamed rivals. Such language may play well with a domestic audience, but analysts note that it has done little to weaken Canadian resolve; if anything, it has hardened it.