Donald Trump and Canadian Prime Minister Mark Carney have never been among contenders to open a mutual admiration society. But over the weekend, their relationship descended to new, uncharted depths of mutual loathing.

The collapse of trade talks between the two North American powers was projected by both governments as a disaster of each other’s making. But in reality, Trump has far more to lose politically over the short term than Carney, with vast punitive tariffs being applied on American trade with and from Canada that could cause fresh US economic dislocation and inflation just 70-odd days before November’s midterm elections.

Shortly after 1am on Sunday, Trump fumed that “Canada wants the benefits of being a State, without being one!!!”. On Truth Social, he insisted that successive Canadian governments “have charged our great farmers, for many years, massive amounts of Tariffs. No more!!!”

But Carney gave as good as he got. In stark contrast to most other world leaders who continue trying to find ways to appease the authoritarian in the White House, the Canadian Prime Minister treated Trump as a naked emperor leading a government of total amateurs.

“They asked too much and offered too little”, he told reporters on Saturday. “You’re at war when you get attacked. We got attacked”, he claimed, adding: “We cannot accept what they’ve offered and will not give what they demand.”

Describing the Canadian negotiating team as “unified…everyone in the loop, everyone knows what our objectives are”, Carney told reporters, “you cannot say that about the US administration”. Effectively confirming widespread reports that Jamieson Greer, the US Trade Representative (USTR), and Commerce Secretary Howard Lutnick were at loggerheads within the Trump administration over key aspects of the negotiations, Carney chose to walk away from the table.

Doug Ford, Ontario’s premier and leader of the centre-right Progressive Conservative Party, was even less diplomatic. “President Trump is the type of person that would steal your lunch money the first day. He’d steal the toque off your head the second day, and the third day he’d steal your running shoes. He is not to be trusted whatsoever,” he told reporters as he credited Carney’s tough approach and urged the country to unite around him.

Lutnick is being pointed to as the main source of the talks’ demise. In April, with his trademark cocksure garrulousness, he mocked Carney publicly during an appearance at a Washington conference, accusing the Canadian government of deploying “the worst strategy I’ve ever heard…They suck”. Later, a US Department of Commerce spokesperson claimed Lutnick was referring to “how Canada sucks off of our $30trn (£22trn) economy”, a claim that suggests the White House views trade with Canada as being similar to negotiating with leeches.

An open backer of Trump’s repeated claims that Canada must become America’s 51st state, Lutnick took particular umbrage over exceptions that had already been discussed by the two governments regarding metals tariffs. He also reportedly pulled the rug from beneath a preliminary agreement that was negotiated by Greer’s team at USTR, claiming it had been “sprung” on him.

For their part, the Americans accuse Ottawa of engaging in a series of last-minute demands (“a cornucopia of caprice”, said one lawyer close to the administration), with Canada claiming that Washington sought to control its sovereign ability to strike third-party trade deals with other countries.

Amid deep recriminations, the trade war between the two countries is now suddenly intensifying, with 50 per cent American tariffs being applied to $20bn (£14.7bn) of Canadian imports, which include dairy, cement, wine and even hockey equipment. Separate existing tariffs on Canadian steel, aluminium, lumber and cars will remain in place.

Carney, in turn, plans to reveal details of his countermeasures against the United States within the next few days, after Greer told Fox News that the US had no plans to resume talks.

For Trump, the impasse comes with significant political risk. Despite his constant denials, US tariffs are passed on to American consumers in the form of higher prices. Very few importers or manufacturers agree to absorb the costs. Research by the Federal Reserve Bank of St Louis identifies a clear correlation between tariffs and inflation, arguing that Trump’s trade duties have become “an important driver of the persistent rise in consumer prices”.

With most American voters telling pollsters they are worse off than they were before Trump returned to power, the state of the economy is expected to be a huge driver of turnout in November’s midterms. Democrats have established a clear lead over Trump with regard to the economy, and now the imposition of fresh tariffs on the country’s northern neighbour can only put fresh pricing pressure on consumers.

Trump’s ire with Carney may fuel the defeat of his fellow Republicans at the polls in November. If so, the Canadians will be having the last laugh.