Canada has promised dollar-for-dollar retaliation from September 8, pushing two deeply integrated economies further into a trade war. The immediate exposure may represent only about 5 per cent of Canada's annual exports to the United States, but that understates the wider consequences. American importers pay these tariffs, leaving businesses to absorb the expense or pass it on to customers. Construction companies, retailers, manufacturers and farmers could consequently face higher costs when households remain acutely sensitive to prices. Protectionism may sound attractive when presented as making another country pay, but its political appeal diminishes when consumers discover that part of the bill has landed on them.

More troubling is Washington's decision to invoke Section 338 of the Tariff Act of 1930, a Depression-era provision allowing duties of up to 50 per cent against countries judged to discriminate against American commerce. The broader Smoot-Hawley tariff regime became synonymous with the protectionist spiral that worsened the collapse in global trade during the Great Depression. Retaliation still has a dangerous tendency to acquire momentum. Canada plans countermeasures covering steel, dairy, appliances, agricultural equipment, pulp, paper and electronics, exposing American exporters to pressures Washington is imposing on Canadian producers. Also concerning is that some goods previously protected under the US-Mexico-Canada Agreement. Trade agreements matter because they provide businesses with predictability. If their protections can be overridden whenever political negotiations fail, companies will reconsider investment decisions, suppliers and production networks built around those rules. The damage then extends beyond individual tariffs to confidence in North American commerce.

Trump's strategy also carries growing domestic political risks. Tariffs have already complicated planning and contributed to inflationary pressures, while the conflict with Iran has introduced another source of price instability. Adding steep duties on goods from America's closest trading partner could compound those pressures in a midterm election year dominated by concerns over affordability. Canada, meanwhile, has learned that concessions do not necessarily guarantee lasting relief, making Ottawa less willing to accommodate demands. The United States has every right to challenge unfair trade practices, just as Canada must accept reciprocal obligations. But durable economic relationships require negotiation, enforceable rules and proportionate remedies, not a contest to erect higher barriers. Tariffs can create leverage, but repeated use against allies encourages alternative supply chains, weakens trust and imposes uncertainty on businesses. Washington may hope economic pressure will force Ottawa back to the table on American terms. It must also reckon with the possibility that the casualties will ultimately be American companies, workers and households paying more for goods that once crossed their border with comparatively little friction.