The era of deep economic, security and military ties between Canada and the United States "is over," Prime Minister Mark Carney said Thursday, after President Donald Trump announced steep auto tariffs. "The old relationship we had with the United States based on deepening integration of our economies and tight security and military cooperation is over," Carney said.
If you’re trying to build domestic manufacturing capacity in a specific industry in which many other countries are competitive, placing tariffs on foreign products in that specific sector can encourage people to buy local until your manufacturers are competitive in the global market.
Similarly, if a foreign country is flooding your market with an excess of some product (dumping) and it’s depressing the price of that product and putting your domestic manufacturers out of business, tariffs can help protect them while you work through treaty processes like WTO complaints.
Trump is doing neither of those things. Blanket tariffs are more likely to collapse your economy than grow it (see: Smoot-Hawley). His tariffs on specific products like steel and aluminium are unlikely to grow American manufacturing capacity in those sectors. Modernizing steel manufacturing in the US would take decades. Aluminum smelting is really energy intensive, so US aluminium producers can’t compete very well with Canadian aluminum producers because Canadian producers have access to cheap and plentiful hydro-electric power. During his last term, steel and aluminium smelting capacity in the US actually shrank and the higher costs of materials in downstream manufacturing put hundreds of thousands of people out of work.