Among the eight "Great Decisions" discussions the Foreign Policy Association chose as 2018 topics is "The Waning of Pax Americana." Only the FPA posed the phrase with a question mark. But after tense sessions between President Donald Trump and other world leaders at last month's G-7 summit in Canada and this week's NATO Summit in Belgium, an exclamation point — or even a period — might be more appropriate punctuation.

Some might argue that Pax Americana — defined by the FPA as "the liberal international order that was established in the wake of World War II" — was waning even before the current turbulence, with China's rise just one among many jolts to the postwar order largely built by — and for — the U.S.

But after scrapping pacts like the Paris climate accord, the Iran nuclear deal and the proposed Trans-Pacific Partnership (TPP), as well as challenging NAFTA and other multilateral agreements and international institutions, Trump may have accelerated the trend.

"By going it alone — 'America First' — we are alienating some of our allies, and in many cases ending up isolated and with less influence than we had," said Tom Hanson, a former Foreign Service officer who is now diplomat in residence at the University of Minnesota Duluth.

Hanson, who presented his perspective on Pax Americana at a Global Minnesota event on Wednesday, added that "we created a structure, we had a very advantageous position within it, we exported it economically, we stood up for free markets, we spent a lot on our military [based] on it."

Presidents presiding over Pax Americana came from both parties. Tactics shifted, but the fundamentals didn't. But Trump "doesn't believe in Pax Americana; he believes in 'America First' and economic nationalism," said Mark Simakovsky, a nonresident senior fellow at the Atlantic Council's Eurasia Center.

Simakovsky, a former Europe/NATO chief of staff in the Office of Secretary of Defense for Policy in the Obama administration, said in advance of the troubled Brussels summit that Trump could just try to take credit for every NATO nation increasing investment in defense — even though the decadelong commitments were wrangled during the Obama era. "But I don't think he's interested in a victory lap," Simakovsky said. "I think he's interested in further exacerbating the tension, either for leverage or to address a political audience at home because it's popular to bash Europeans, it's popular to bash allies."

And sure enough, after caustic comments aimed at allies like German Chancellor Angela Merkel, Trump left for London only to roil, if not spoil, the "special relationship" with Britain by telling the Sun tabloid that he didn't approve of the "soft" Brexit strategy of Prime Minister Theresa May, all the while praising her Tory rival Boris Johnson, the former foreign minister whose recent resignation rocked May's government.

Then, confronted with the controversy his comments caused, Trump tried a familiar dodge by calling it fake news even though there are real recordings of the interview.

Eventually, as he did in Brussels, Trump tempered his tone. But as at the G-7 and NATO summits, substantial damage was done.

These serial setbacks are "deeply damaging to the institutions and more importantly to America's capacity to lead, because leadership is first and foremost about followership," said Ivo Daalder, president of the Chicago Council of Global Affairs. Daalder, who served as the U.S. ambassador to NATO from 2009-13, added that "our ability to lead globally has not been eroded completely. It can be rebuilt. But every day that goes by and every summit meeting or international meeting as we've seen at the G-7 and now the NATO summit in Brussels that sees the United States not leading but standing alone is a day that makes it more difficult to come back to the fundamental leadership role that the United States has played since 1941."

And global leadership is needed more than ever. Not just to respond to adversaries, but also to ostensible allies that are degrading democratic norms, like the increasingly illiberal leaders in some Eastern European nations.

After his British visit, Trump heads to Helsinki for a summit with Vladimir Putin, president of a nation with which the U.S. has had a decidedly un-special relationship. And yet Trump said before Brussels that "frankly, Putin may be the easiest of them all. Who would think? Who would think?"

Not those hoping to hold the alliance together in response to Russia's revanchist ways. Because strength in numbers will be required to respond to Moscow's menace of military provocations and asymmetric threats to Western elections — as evidenced by Friday's indictment of 12 Russian intelligence officers who allegedly hacked the Democratic National Committee and the Clinton campaign during the 2016 election.

"We are in competition globally with China and Russia, and the one thing we have that they don't is allies," said Daalder, who added that the U.S. has had "partners who were willing to stand with us economically, politically and in a way that Russia and China don't, and that's our biggest advantage. And to give that away is something that will make it more difficult for us to compete effectively with the Chinese and the Russians going forward." Or, as the European Council's top diplomat, President Donald Tusk, said less diplomatically on the eve of the NATO summit: "Dear America, appreciate your allies. After all, you don't have that many."

Appreciating — and keeping — those allies requires an emphasis on internationalism. Introspection about our democracy may help, too.

"We've been very active in promoting our values," Hanson said. "But perhaps all the while letting those values get a little frayed at home," he said. "So I think a key to our power and policy going forward will be to get our own act in order to again become a model for the kind of values for democracy that we would hope."

As for the more profound question — or question mark — about the waning of Pax Americana, Hanson said in an interview, "It's not a question mark: The world is changing, the relative weight of the economies of large countries, China especially, are shifting and you really can't expect the world to stay frozen 70 years later."

Indeed, international eras shift, and Pax Americana has had a relatively extended run during a period of dynamic demographic, technological, social and political change.

But preserving portions of the postwar order is in America's best interest, so U.S. leaders at all levels should shore up our global alliances and our democracy right here at home.

John Rash is a Star Tribune editorial writer and columnist. The Rash Report can be heard at 8:10 a.m. Fridays on WCCO Radio, 830-AM. On Twitter: @rashreport.

Once a month, the theme of this column is determined by the "Great Decisions" dialogue on foreign policy, conducted in partnership with the nonprofit citizen engagement organization Global Minnesota. Want to join the conversation? Go to globalminnesota.org.