By Baba Abdullahi Machina
The future of Europe’s security architecture has become an increasingly pressing concern, particularly as U.S. President Donald Trump expressed scepticism about America’s commitment to NATO. Since its establishment in 1949, NATO has served as a collective defence treaty among member states—including the UK, France, Germany, Italy, Norway, and others—under U.S. leadership. However, if the U.S. were to withdraw, Europe would face a critical choice: should it maintain NATO without American support or develop an entirely new defence framework?
The Financial and Strategic Challenges of Maintaining NATO.
One of the biggest obstacles Europe would face in sustaining NATO without U.S. involvement is financial. Currently, the United States provides approximately 50% of NATO’s funding, and no single European country has the economic capacity to single-handedly replace that contribution. Even Europe’s largest economies—France, Germany, and the UK—are struggling with economic challenges, including inflation, energy crises, and slowing growth, partly exacerbated by the fallout of Russia’s invasion of Ukraine.
For decades, Europe has depended on the U.S. for security guarantees, allowing most NATO members to underinvest in their defence capabilities. If Washington were to withdraw, Europe’s vulnerabilities would be laid bare, particularly in light of the growing threat from Russia. While European nations could theoretically increase their defence budgets to compensate for the loss of U.S. support, doing so would require a major shift in economic priorities and political will.
A study by the Bruegel think tank and the Kiel Institute estimates that Europe would need to spend around €250 billion annually—approximately 1.5% of the EU’s GDP—to mobilise an additional 300,000 troops to maintain a credible defence posture without U.S. assistance. The European Commission, under President Ursula von der Leyen, has proposed a strategic defence initiative that aims to mobilize €800 billion to strengthen Europe’s defence capabilities. However, such an effort would take time to implement, and questions remain about whether European nations would be willing to shoulder the costs.
If NATO without the U.S. is financially unsustainable, Europe might explore alternative defence arrangements. One option would be to create a European-led defence alliance, independent of NATO, that integrates the military capabilities of EU members and other European nations. This would require deeper defence cooperation, shared command structures, and significant investment in military hardware and infrastructure.
Another potential approach is the formation of a “Coalition of the Willing”—a group of European nations committed to security cooperation outside of formal NATO structures. The UK, for example, has taken a leadership role in supporting Ukraine, and similar coalitions could emerge to counter Russian aggression. However, such coalitions raise legal and strategic concerns. Past experiences—such as the 2003 invasion of Iraq, which was carried out without UN authorization—show that coalition-based military actions can be controversial and divisive.
The Role of the U.S. in Future European Security
A critical question is whether Europe, even if it develops a new defence framework, would seek to involve the U.S. in some capacity. Would the U.S. be willing to participate in a European-led security initiative without being the dominant force? If Washington continues on an isolationist foreign policy trajectory, Europe may have no choice but to build its independent security infrastructure.
At the same time, history suggests that a full U.S. withdrawal from European security is unlikely. Even if Trump or another U.S. leader pursues disengagement, geopolitical realities—particularly the threat posed by Russia—may eventually pull America back into European security affairs.
If the U.S. were to withdraw from NATO, Europe would face a difficult but necessary decision: either increase defence spending significantly to maintain NATO or develop an alternative security architecture. While economic challenges make sustaining NATO without U.S. support difficult, European leaders may need to rethink their approach to defence in a rapidly changing global landscape. The ultimate solution may lie in a mix of increased military investment, deeper European cooperation, and strategic engagement with allies beyond the continent.
Baba Abdullahi Machina is a Public Policy Analyst.
