Former U.S. ambassador to NATO Ivo Daalder has warned that the alliance is in its worst crisis in decades, bluntly declaring “NATO is broken.” He argues recent clashes between President Trump and several European governments over the Iran crisis have exposed a severe erosion of trust and prompted debate over whether Europe could or should operate NATO without U.S. leadership.
How we arrived here
Daalder and other analysts point to a mix of rhetoric and concrete actions. Beyond insults and periodic threats to quit the alliance, Trump has called NATO a “paper tiger” and suggested it might not back the United States in a conflict with Iran. More consequential, say European officials, were decisions by some capitals to deny U.S. forces use of bases or airspace for offensive operations—moves that signal unwillingness to be drawn into a U.S.-led campaign and underscore a growing perception of the United States as an unreliable partner.
NATO leaders have sought to play down the split, stressing common concerns about Iran even as allies’ responses differ. Still, the standoff has intensified a broader conversation in Europe about capability gaps and political will.
Could the U.S. leave NATO?
A presidential decision to withdraw would face legal and political obstacles. Congress passed legislation in 2023 sponsored by then-Senator Marco Rubio requiring two-thirds Senate approval for any U.S. exit, complicating an entirely unilateral pullout. The Washington Treaty itself includes Article 13, permitting a member to withdraw after 20 years with one year’s notice—an option never used. Even short of formal withdrawal, a president could severely weaken NATO by withdrawing troops, withholding personnel from NATO commands, curtailing institutional support, or declining to fill senior U.S.-held posts such as Supreme Allied Commander Europe.
What if the U.S. role faded?
The U.S. supplies the alliance’s largest, most advanced arsenal and major manpower, as well as critical capabilities in space, intelligence, surveillance and reconnaissance (ISR), and command-and-control. Analysts say NATO would struggle to sustain credible high-end military power without Washington. At the same time, European efforts to strengthen defense capacity and leadership are already under way.
A study by the International Institute for Strategic Studies urged European leaders to map the military, financial and industrial steps needed to substitute for U.S. contributions. It warned of major shortfalls replacing key platforms and personnel, particularly in space and ISR, and noted the need to fill many senior command roles currently held by Americans. The report estimated the extra cost to Europe at roughly a trillion dollars, on top of existing increases in defense spending.
A divided European response
Opinions in Europe vary. Nick Witney of the European Council on Foreign Relations has argued that Europe can survive without U.S. primacy—though he would prefer continued American troop presence. French President Emmanuel Macron has explored deeper nuclear cooperation outside NATO’s collective nuclear command, reflecting moves to strengthen autonomous deterrence. Smaller allies such as Estonia have shown public support for the U.S., with leaders emphasizing reciprocity and reassurance for populations worried about Article 5.
Dutch Prime Minister Mark Rutte has backed measures to pressure Iran and sought to reset transatlantic ties through diplomacy. Meanwhile, Trump has continued to criticize European reluctance and made characteristic aside comments about Greenland during meetings with allied leaders.
The bigger question
The current debate combines immediate political friction with larger strategic decisions: can Europe marshal the finances, industry and political consensus to replace significant U.S. contributions, or will transatlantic relations be repaired before such a reconfiguration becomes necessary? How that balance is resolved will shape NATO’s future and the broader security architecture of the Euro-Atlantic region.