December 5, 2022 11:11 AM EST

When Joe Biden flew to the wind-swept coast of Cornwall, England, for his first major meeting with leaders of allied nations in June 2021, he wanted to footstomp that the Trumpian era of publicly berating allies and eschewing international cooperation was over. He later recalled declaring to a meeting of foreign leaders, “America is back.” In response, French President Emmanuel Macron and three other leaders asked him the same question: “For how long?”

A year and a half later, that looming anxiety among European allies hasn’t gone away. Even after Biden took the lead in corralling a unified response to Russian President Vladimir Putin’s war in Ukraine and increased American troop presence in Europe, there’s a lingering sense of unease that the long-term U.S. commitment to Europe’s security remains too vulnerable to the unpredictable gusts of American politics.

The midterm campaigns last month were a wakeup call. Several Trump-backed candidates expressed skepticism over U.S. military involvement in Ukraine. European leaders and diplomats were relieved when that isolationism didn’t overtake Congress amid a Republican red wave, but some of those candidates did win and many others came close.

Europe’s leaders are looking nervously at what the 2024 Presidential election cycle may mean for U.S. support for the North Atlantic Treaty Organization, which former President Donald Trump has long criticized and wanted to walk away from. And that’s added to the urgency of efforts to get the U.S. to bolster NATO as much as possible in the next two years, before a possible shift in the political winds.

“There was more concern before the outcome of the midterm elections,” says François Heisbourg, a strategic analyst and advisor to the Foundation for Strategic Research, a think tank in Paris. “Now the concern shifts further down the line and changes in nature.”

That concern has played into Macron’s hands, who was the guest of honor last week at Biden’s first state dinner and has spent years insisting that Europe needed to rely less on the U.S. military for its own defense. On Dec. 13, Macron will be hosting an international meeting in Paris, where he hopes to bolster support for Ukraine and NATO.

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Already NATO has strengthened its defenses, increasing the troop presence along Russia’s western flank from four battle groups to eight. NATO countries are also looking at upgrading missile and aircraft systems and buying more ships and maritime defense equipment. Sweden and Finland, two countries close to Russia, are moving forward with joining the alliance, ending 73 years of reticence to sign on to the joint defense pact. And on Nov. 29, the foreign ministers of NATO countries met in Romania’s capital, Bucharest, and reaffirmed NATO’s “open door policy,” including a willingness for Ukraine to eventually join the alliance, a stance that has incensed Putin in the past.

Putin’s tank blitz into Ukraine in February set off an effort to shift NATO’s strategic posture away from only being equipped to respond to an incursion by Russian troops, and more toward mobilizing to deter a future invasion by creating enough of a military presence along Russia’s border. The strategy is known as “deterrence by denial.”

Sophia Besch, a fellow at the Carnegie Endowment for International Peace, says the strategic shift in Europe came about in part out of fear that the political changes inside the US may eventually erode American commitments to NATO. “If the US attention eventually shifts away from Ukraine and Europe, there is a sense, particularly in France, that strengthening the European pillar in NATO matters,” she says.

That means getting European militaries to build up the airlift, logistics and maritime fighting power that the U.S. currently provides.

As Republicans prepare to take control of the House in January, the party’s leaders are signaling that they will be looking more closely at US funding for the war in Ukraine. The likely new Speaker of the House, Rep. Kevin McCarthy, said in October that Americans wouldn’t support writing a “blank check” on Ukraine. That will likely mean pressure from House Republicans to beef up scrutiny on future rounds of economic assistance going to Ukraine, says Daniel S. Hamilton, a fellow at the Brookings Institution. Nonetheless, there remains strong bipartisan support in Congress for providing direct military assistance to Ukraine’s war effort. “If you really look hard, there is a consensus among the Republicans in the Senate and the House on lethal aid to Ukraine,” Hamilton says.

For now, in Europe, the political parties in power are largely backing Ukraine, with the exception of the leadership in Hungary, says Heisbourg. “You have the division within practically every country, including the US, with those who think this should be settled as soon as possible, taking into account the interests of Russia,” Heisbourg says. “But apart from Hungary there is nowhere where that part of public opinion is actually in power.”

Macron is expected to further push for strengthening European commitments to NATO at the international conference on Ukraine he’s hosting in Paris next week. Looming over those talks is the question of how long the war in Ukraine will last, and the terms under which Putin and Ukraine’s President Volodymyr Zelensky might suspend the conflict. Putin has escalated the war in recent weeks, sending volleys of missiles to destroy water and heating systems across Ukraine as winter sets in. Zelensky has continued to hold to the line that his country remains committed to fighting until Russian troops retreat from Ukrainian soil, including Russian forces in Crimea, which Putin illegally annexed in 2014.

During a press conference at the White House on Thursday with Macron, Biden said he would be willing to sit down with Putin, if Putin was “looking for a way to end the war.” But Biden said he wouldn’t talk to Putin without closely consulting his NATO allies. “I’m not going to do it on my own,” Biden said.

— WITH REPORTING FROM VIVIENNE WALT/PARIS

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