Vladimir Putin may have taken Crimea for Russia, but in Washington on Wednesday the talk was of US annexation of Canada – all 4m square miles of it.

That at least was the “thought experiment” conducted by the Woodrow Wilson Center, a prestigious DC thinktank, which hosted a debate featuring the author of a book advocating political union of the two North American neighbours.

Diane Francis, a conservative Canadian newspaper columnist with dual US citizenship, says her call for the “merger of the century” has been listened to more seriously south of the border where she claims to have received complimentary letters from Hillary Clinton and Jeb Bush.

“In Canada, people are horrified,” admitted Francis, before discussing how its 13 provinces and territories could become US states – but why Quebec might instead choose to become a semi-independent commonwealth, “a bit like Puerto Rico”.

Though few, if any, of those on Wilson’s panel of experts believed it could ever happen, the whimsical nature of their debate belied more serious discussion of the merits of European-style border reform and growing talk of greater economic integration even among North American political leaders.

At a summit in Mexico last month celebrating the 20th anniversary of the North American Free Trade Agreement, Canadian prime minister Stephen Harper and US and Mexican presidents Barack Obama and Enrique Peña Nieto all urged regional trade harmonisation as a counterweight to China and agreed on a new fast-track border scheme for “trusted” travellers.

Francis simply argues that Canada could travel much faster down this route than Mexico.

“I think we are already merging,” she said at Wednesday’s debate. “We should just get on with it and take away the border. My solution to fixing the border problem is just to get rid of it.”

Her thesis rests partly on the claim that the two countries have become more alike in recent decades as the US grows more liberal and Canada less parochial, but she admits the notion of 35 million new Democratic-leaning voters might prove a deal-breaker for many Republicans, as well as a few politicians north of the border.

“Canadians would act like a fabric softener for US politics,” claims Francis, allowing reforms like universal healthcare to take root, while also providing a pressure valve for conservative Americans and Quebecois nationalists alike.

In return, goes the argument, American conservatives could find allies in Alberta and the Arctic and help drive North American energy production, both fossil fuel and renewable, in ways that would make current arguments over the Keystone oil pipeline redundant.

Nevertheless, Francis admitted her idea of Canada joining the US as a series of new federal states is mainly a polemic designed to draw attention to her more concrete proposals for economic integration.

“The politics of this probably make a full union impossible,” she conceded.

“At best, my guess is that maybe we can get rid of the border and move towards the next step, which is a customs union.”

The panel agreed, concluding that the thought experiment was a “policy provocation” pointing more to lessons that can be drawn from the European Union rather than, say, the unification of Germany.

“There is a lot that America and Canada can learn from Europe, but even there the dream of a federal Europe has largely been replaced with one of greater co-operation,” said Michael Geary, a Wilson Center fellow.

“While the European Union in its form today is not one I would recommend, aspects of the EU policy framework could benefit the Canadian American relationship.”

But, conceded Geary, a book called “Enhanced Co-operation” might not sell as well as one called “Merger of the Century”.