(The Hill) — President-elect Donald Trump has doubled down on his suggestion of a merged United States and Canada following Canadian Prime Minister Justin Trudeau’s decision to resign.

Some have shrugged off Trump’s suggestion that Canada should “become the 51st state” as an old joke or mere posturing, while others dismiss it as a bad political idea given Canada’s blue leanings. 

But Trump on Tuesday threatened “economic force” to annex the U.S.’s neighbor to the north. Together with talks of buying Greenland and controlling the Panama Canal, the comments suggest he’s aiming to expand U.S. power after he takes office this month. 

The concept, though, continues to be largely unpopular among Canadians. And with Trudeau exiting the political stage, it’s unclear what impact Trump’s remarks will have on the U.S.-Canada relationship under new leaders.

Here’s what to know about Trump’s calls to merge the U.S. and Canada:

Annexation efforts date back to early U.S. history

The idea of a union between the U.S. and Canada dates back centuries when early American leaders invaded Quebec during the American Revolution. A few decades later, the U.S. unsuccessfully invaded Canada during the War of 1812 amid frustration over the Royal Navy’s moves to bring American sailors into their own ships. 

“Canada and the U.S. fought a war over this in 1812,” said Matthew Lebo, a political science professor at the University of Western Ontario and a visiting professor at McGill University, as he shrugged off Trump’s idea of a renewed annexation push. 

Annexation and invasion fears continued throughout the American Civil War and amid the U.S. push for expansion and Manifest Destiny, or the idea that the U.S. was destined to control the continent. But those fears ended as the two nations shifted to become “fierce allies” in the 20th Century, said Duane Bratt of Mount Royal University, a political science professor with a focus on Canadian foreign policy.

“NORAD was formed. NATO was formed. Canadians fought with Americans in World War I and in World War II, and in Korea and in the Gulf War,” Bratt said. “American soldiers died for Canada. Canadian soldiers died for the United States.”

Today, Canada and the U.S. have been steadfast military and economic partners for more than a century. But some wonder whether Trump’s jabs against his country’s longtime ally could hint at hopes for the U.S. to control more of the Western Hemisphere. 

“Do we want to go back to 1812, the 1860s? Maybe Trump does, but I’m not too sure Americans do, or Canadians do,” Bratt said. 

A merger is unpopular in Canada

Trump’s talk of annexation and merging is unpopular with Canadians — and so is the American president-elect.

A recent Leger poll, reported by The Canadian Press, found a whopping 82 percent of Canadians were opposed to the idea of joining the U.S. as the next state. Another Leger poll from October found that, when asked which American candidate they’d support if they could vote in the 2024 race, roughly two-thirds of Canadians backed Vice President Harris and just 21 percent supported Trump.  

“I don’t think he realizes that Canada would be a Democratic state, that we would be a blue state the size of California,” Bratt said. 

Then there’s the logistical thorniness. Canada is a constitutional monarchy, compared to the U.S. republic, and already split into 10 provinces. 

“It might look like Canada and the United States have a lot in common, but a quarter of Canada speaks French, and the province of Quebec still isn’t part of the Canadian Constitution. They don’t want to be part of the American Constitution,” Lebo said. 

Still, some see merit in what the president-elect is suggesting. “Shark Tank” star Kevin O’Leary, who recently spent time at Trump’s Palm Beach hub, told “The Hill” on NewsNation that there are “some very interesting concepts” within that idea, including an “economic union.” 

Many see Trump’s talk as trolling

Given the history between the two countries and the complexities of any possible merging, observers have largely shrugged off Trump’s talk as just jokes and boasts before he re-enters the Oval Office. 

Canadian Public Safety Minister Dominic LeBlanc, who attended a dinner at Mar-a-Lago last month where Trump reportedly made a “51st state” comment, told The Associated Press that the remarks were clearly in jest. And Gerald Butts, a former top adviser to Trudeau, wrote in a post on LinkedIn last month that Trump had dropped the “51st state” line “a lot” with the prime minister during his first term without any bite. 

“He’s doing it to rattle Canadian cages,” Butts said. “When someone is trying to get you to freak out, don’t. #protip.”

But Trump on Tuesday seemed to indicate he wasn’t bluffing.

The president-elect in a press conference ruled out using military force to annex and acquire America’s neighbor to the north but threatened “economic force” to get it done. 

“Because Canada and the United States, that would really be something. You get rid of that artificially drawn line and you take a look at what that looks like, and it would also be much better for national security,” Trump said.

He also suggested hockey great Wayne Gretzky should run for prime minister of Canada, quipping that the title should be “governor” instead. 

“There isn’t a snowball’s chance in hell that Canada would become part of the United States,” Trudeau said after the presser. “Workers and communities in both our countries benefit from being each other’s biggest trading and security partner.” 

Trudeau’s exit complicates things for Canada

Trudeau, who has been at Canada’s helm for nearly a decade, resigned as prime minister on Monday after mounting internal frustration and problematic polls for the ruling Liberal Party. The move was expected, experts said, but the timing of the announcement notably comes after Trump’s tariff threats and his jabs labeling Trudeau as Canada’s “governor.” 

After Trump threatened 25 percent tariffs to urge Canada to crack down on border security and drug trafficking, Trudeau jetted to Trump’s Mar-a-Lago residence in Florida — a move that contributed to some criticism of Trudeau as weak. 

Trudeau’s exit “complicates Canada’s response,” because it leaves him a lame duck prime minister, Bratt said, while Conservative Party leader Pierre Poilievre vies to end Liberal rule in the country’s next election.

“Between now and early May, Canada is kind of rudderless,” Bratt said. 

“Yes, we have a prime minister with all the powers and authority that go with that office, but without the political legitimacy,” he added. “And now we’re dealing with potentially an existential, economic and perhaps political threat being posed by what we had thought was our closest ally via the United States, and we are in a very weak position to push back because of the domestic political crisis in this country.”

After Trudeau’s resignation, Trump re-upped his claim that “many people in Canada LOVE being the 51st State” and argued, “Justin Trudeau knew this and resigned.” 

So if Trump is serious about upping pressure on its ally, he’ll have to navigate the issue with new leaders soon, and many in Canada have soundly rejected his calls. 

“My message to incoming President Trump is that first and foremost, Canada will never be the 51st state of the U.S.,” Poilievre said in an interview with CTV late last month.

Trump doubling down on expanding U.S. power

Trump’s jabs at Canada come as he pitches a U.S. takeover of Greenland and the Panama Canal. 

In his Tuesday presser, when he nixed the possibility of military force against Canada, Trump said he couldn’t promise not to use military or economic coercion to control either Greenland or the Panama Canal, because “we need them for economic security.” 

Though experts are still uncertain about how much stock to put in Trump’s threats, his talk of the three regions together has led some to believe he’s serious about expanding U.S. power in his second term, whatever that may look like.

“By making threats like this, he might be scaring some companies about whether they’re choosing to invest in Canada versus the United States,” Lebo said. “And I’m sure he wants to put his thumb on the scales for the next Canadian election.” 

Bratt said he thinks Trump’s Tuesday presser signaled a shift in the president-elect’s stance. 

“At what point is a joke not a joke? He went from talking about ‘governor’ Trudeau and becoming the 51st state to, today, talking about economic coercion, economic force. I guess we should just be happy he wasn’t talking about military force,” Bratt said.