Editor's note: Zhang Jing is the editor-in-chief at the Maclmlen Studio. This article reflects the author's opinions and not necessarily those of CGTN.

The trade dispute between Canada and the US entered a new phase Tuesday as Ottawa announced retaliatory tariffs on 27.6 billion Canadian dollars'worth of US imports, matching Washington's latest duties dollar for dollar and rate for rate.

The move follows US tariffs of up to 50% on 27.6 billion Canadian dollars'worth of Canadian goods. The measures took effect August 22 and affect roughly 5% of Canada's exports to its largest trading partner.

Canada's counter-tariffs, announced August 25 and effective September 8, will impose duties of 15, 25 and 50% on around 700 US’s products, including steel, dairy products, appliances, agricultural equipment, pulp and paper and electronics.

Ottawa has also announced a 7.5 billion Canadian dollar support package for affected businesses and workers, including financing and liquidity support for small and medium-sized companies.

The escalation is testing a bilateral trading relationship built over decades on integrated supply chains, cross-border investment and preferential market access.

The immediate economic impact may be relatively contained because only about 5% of Canadian exports to the US are directly affected. The direct hit is moderate. But the broader significance goes beyond the value of the goods targeted.

Washington invoked Section 338 of the Tariff Act of 1930 for the latest measures. The rarely used provision has not been invoked in this way for roughly a century. Washington also decided not to provide exemptions under the North American free trade framework for the affected goods.

For Canada, the bigger concern is what the dispute means for the predictability of a relationship on which much of its industrial economy has been built.

Businesses have long relied on relatively stable trade rules when making investment, manufacturing and supply-chain decisions. Repeated changes in tariffs and exemptions make those calculations harder and turn uncertainty itself into an economic cost.

Ottawa's response marks a shift in the dispute. Canada is no longer simply absorbing additional US tariffs while seeking a negotiated settlement, but is imposing targeted measures of its own.

The Canadian government said it suspended trade negotiations after concluding that the latest US proposals were not in Canada's economic or national interest. Finance Minister François-Philippe Champagne said Canada's response would match the American measures "dollar for dollar, rate for rate."

But retaliation carries domestic costs. Tariffs on US machinery, equipment and intermediate products can raise expenses for Canadian companies, with some costs eventually passed on to consumers. The 7.5 billion Canadian dollar support package reflects Ottawa's recognition that businesses and workers could face growing pressure if the dispute continues.

The automotive sector could be one of the biggest tests.  

The latest 50% US tariffs do not directly apply to automobiles, which remain subject to a separate 25% tariff introduced earlier this year. However, the new measures affect chemicals, plastics, electronics and other products used throughout the automotive supply chain.  

Vehicles meeting North American trade rules receive an exemption for their US content. A typical Canadian‑made vehicle therefore faces an effective tariff of around 12.5% rather than the full 25%.  

The industry's deep integration means the impact cannot easily be confined to one side of the border. Canadian and US factories form part of the same production network, with vehicles and components crossing the border multiple times during manufacturing. Higher costs in Canada can therefore flow through to US assembly plants, suppliers, dealerships and consumers.

Energy presents a different picture.

Canadian oil, natural gas and electricity were excluded from the latest US tariffs. Jiang described energy as a "protected core" of the bilateral economic relationship, reflecting the extent to which the US relies on Canadian supplies.

Canada is the largest foreign supplier of crude oil to the US, while natural gas and electricity also move through extensive cross-border infrastructure. Replacing those supplies in the short term would be considerably more difficult than switching suppliers for many manufactured goods.

Yet Canada's dependence on the US market remains a longstanding vulnerability. Energy is one of Canada's largest exports, and geography and infrastructure have historically directed much of that production south of the border.

The dispute is therefore likely to add urgency to Canada's efforts to diversify its trade relationships.

Jiang believes the process has already gained political momentum but cautioned that it will be "more like a marathon than a sprint."

The US is likely to remain Canada's dominant economic partner for the foreseeable future. Geography, infrastructure and decades of integrated production mean industries ranging from automobiles and agriculture to energy and manufacturing cannot simply redirect their exports overnight.

Diversification requires new infrastructure, markets, customers and supply chains. It is therefore a long-term strategy rather than an immediate substitute for the US market.

The larger consequence of the dispute may be its impact on confidence in the North American trading system.

Canada and the US exchange hundreds of billions of dollars in goods and services each year, and millions of jobs on both sides of the border are connected directly or indirectly to bilateral trade. Prolonged tariff uncertainty could influence investment decisions even in industries not directly targeted by the current measures.

Companies may postpone investments, reconsider sourcing decisions, increase inventories or seek alternative suppliers to protect themselves against future policy changes. Over time, such adjustments can reshape supply chains and trade patterns.

Modern supply chains depend not only on low tariffs but also on predictable rules. Businesses can adapt to known costs, but uncertainty over whether tariffs, exemptions or trade rules could change abruptly is harder to manage.

The immediate economic damage from the latest measures may remain concentrated in selected sectors. But the longer the confrontation continues, the greater the risk that a tariff dispute evolves into a broader reassessment of one of the world's most integrated bilateral trading relationships.

For Canada, the challenge is to protect its industries while limiting costs to businesses and consumers and building greater resilience over the longer term.

For both countries, the deeper question is whether a trading relationship built on decades of integration can continue to function effectively if the predictability underpinning that integration is increasingly in doubt.

(Cover via VCG)