OTTAWA — The story of the dramatic change in Canada’s global profile — and in the decline of American influence around the globe — might be glimpsed in three telling moments.

Back in 1916, when Canada sent troops to assist Great Britain in World War I but the United States remained on the sidelines, one of the leading songs here carried the jaunty reprise line, “We’re the boys from Canada/Glad to serve Britannia.”

Some 22 years later, in August 1938, Franklin Delano Roosevelt traveled to Kingston, Ontario, to meet Prime Minister William Lyon Mackenzie King and extend a military security pledge to Canada that has persisted for more than three-quarters of a century.

And then, this August, Canada stood aghast as the United States withdrew its troops from Afghanistan in an episode of mass chaos that raised fresh questions about American resolve, dependability and power on the world stage.

In this capital, as in London, Paris, Berlin, Moscow and Beijing, foreign policy experts sensed a power vacuum, for the scene at the Kabul airport seemed to symbolize a fundamental shift in the world order. In abandoning Afghanistan, the United States appeared to be abandoning its role as a global leader.

Those other world capitals have historical experience with charting their own ways in the world that Canada, dominated diplomatically and militarily first by Great Britain and then by the United States, lacks. None of them shares with another country a 5,525-mile border, 120 land crossings and an economic relationship accounting for $1.7 billion in trade each day. And yet nowhere was the midsummer alteration in the power balance felt as strongly as it was here, where it prompted deep concern, deep debate — and determination that Canada needed, finally, to come out from under America’s shadow and assert itself.

The result: Canada now may be freer of another country’s interests and power than at any time in its history.

As Afghanis who worked with Western nations, including Canada, besieged the Kabul airport, five top Canadian diplomats and scholars wrote that the “disastrous retreat from Afghanistan is yet one more development that shows the U.S. has lost the primacy it once enjoyed in international affairs.”

They in essence argued that the nation they had depended upon no longer was dependable. Indeed, the United States increasingly appeared as, in the words of the title of a 1958 novel by the beloved Canadian author Robertson Davies, “A Mixture of Frailties.”

“Without effective U.S. leadership, the onus to address burning international issues falls more heavily on the rest of us in the democratic world,” argued the group, a veritable Canadian diplomatic dream team that included former foreign minister Lloyd Axworthy and former Quebec premier Jean Charest. “The rise of illiberal nationalism and authoritarian rule, the declining self-confidence of liberal democracy, the return of protectionism and trading blocs, runaway nuclear proliferation, global health and climate crises — these are issues that countries such as Canada must now confront if superpowers cannot or will not.”

This view, ignored in Washington and barely noted beyond Canada, nonetheless was the functional equivalent of a diplomatic declaration of independence.

It does not mean that the United States will cease to exercise influence over Canada, withdraw from security arrangements with Canada, stop affecting cultural life in Canada, and end enormously important economic ties with Canada, which account for 16.4% of all American international trade. It does, however, mean that Canada may be more willing than ever to go its own way.

This is not a sudden break. Canada did not join the United States in the Vietnam conflict and did not participate in the 2003 invasion of Iraq. Relations between Prime Minister John Diefenbaker and John F. Kennedy were frosty, and American presidents Lyndon B. Johnson and Richard M. Nixon had contempt for Pierre Elliott Trudeau.

But no prime minister and president had as poor rapport as Justin Trudeau and Donald J. Trump.

“Trudeau and Trump were polar opposites on so many issues, including the vision of what each country’s role was on the world stage,” said Rafael Jacob, an analyst in American politics at the University of Quebec at Montreal.

Trudeau has sought to repair relations with the United States by reaching out to President Biden — whom many Canadians credit with helping to free two Canadians who were detained in China for more than 1,000 days — even as he looks across both the Atlantic and the Pacific.

“Trudeau has been relentlessly pragmatic in dealing with both Trump and Biden as a way of maintaining the benefits of the relationship,” said Geoffrey Hale, a political scientist at the University of Lethbridge in Alberta. “But all the while he has been retaining some discretion to act on his own, and now more than ever.”

Though there always has been a strain of anti-Americanism across the 49th parallel, Canadians generally have thought warmly of the United States. But in the wake of the Trump years, the high rates of COVID-19 in the United States and the siege of the Capitol, many Canadians now are looking across the border not with admiration but with horror.

The decoupling that these episodes prompted has served to amplify a movement that has been underway for two decades.

“There are reasons for the two countries to be close, but broader forces suggest Canada will go its own way,” said Christopher Kirkey, director of the SUNY Plattsburgh Center for the Study of Canada. “After the death of the Soviet Union, Americans felt less of a need for Canada and there was less of a need for Canada to feel tied to the U.S.”

More recently, American actions, in Afghanistan and in trade, have alienated Canadians, who believe the United States is too prone to act unilaterally in international affairs, prompting them to wonder, as Jeremy K.B. Kinsman, former Canadian ambassador to Great Britain, the European Union, Italy and Russia, put it, “if the Biden administration’s allegedly globalist world view is in effect not just a nicer mask for Trump’s ‘America First’ mantra, which has support in Congress, where globalization is still blamed for the loss of American jobs.”

There now is a sense that American troubles are a Canadian opportunity. Put another way: Sometimes in the course of human events, it becomes necessary for one people to dissolve the political bands that have connected them with another.

 David M. Shribman is the former executive editor of the Pittsburgh Post-Gazette. Follow him on Twitter at ShribmanPG.