EU enlargement serves not only European interests but also those of the United States. As Nicholas Lokker argues, expanding the European Union strengthens peace in a vital region and enhances the EU’s capacity to act as Washington’s partner of first resort amid mounting global challenges
In her introductory piece for this series, Veronica Anghel made a compelling case for the European Union to treat enlargement as a strategic necessity. But enlargement is also a strategic necessity for the United States. Washington should recognise its stake in the process and use all available tools to help ensure its success.
The success or failure of EU enlargement will have a major impact on US security and prosperity in the years to come
For more than three quarters of a century, the United States has seen Europe’s fate as inseparable from its own. While the pivot of US foreign policy to the Indo-Pacific under Donald Trump’s administration means that Europe may not be Washington’s top regional priority, its importance for US security and prosperity will nonetheless remain. The success or failure of EU enlargement will have a major impact on each of these interests in the years to come.
As the European Union has progressively enlarged over the decades, so has the zone of stable peace in Europe. Going to war against each other has become unthinkable among the 27 member states and 450 million citizens now comprising the Union. Integrating current EU aspirants in the Western Balkans and Eastern Europe will further bolster European security.
In the Western Balkans, where interethnic tensions have yet to fully subside, EU accession promises to act as 'glue' uniting the region’s different ethnic groups in a larger whole. Successful enlargement can also increase stability in the Western Balkans by helping to transform accession countries into full democracies, which are less likely to go to war with each other. Despite the problem of democratic backsliding among current EU members, the European Union retains very significant leverage in incentivising political reforms prior to accession.
Helping to advance EU enlargement could help Washington satisfy Kyiv’s persistent demands for security guarantees while simultaneously reducing its own share of the burden for European security
Meanwhile, integrating targets of Russian aggression in Eastern Europe — most notably Ukraine — will deepen their security ties to current EU members, strengthening their ability to push back against Moscow’s neo-imperialist project. The Kremlin will need to think twice about attacking a country protected by the bloc’s mutual defence clause, especially given the massive rearmament now underway within the European Union. Given the unlikely prospects for further NATO enlargement, helping to advance EU enlargement may represent an attractive means for Washington of satisfying Kyiv’s persistent demands for security guarantees while simultaneously reducing its own share of the burden for European security.
For Washington, therefore, supporting EU enlargement means supporting long-term peace and security in Europe. Stable European peace reduces the likelihood that a large US military presence on the continent will be necessary in the future, freeing up the United States to focus on the Indo-Pacific.
EU enlargement also makes Europe wealthier. Accession to the bloc — including single market integration, enhanced attractiveness for investment, and access to cohesion funding — has resulted in rapid economic growth for numerous European countries. While current EU members will face tradeoffs in absorbing new member states, the costs will be largely offset by greater opportunities for trade and investment in an enlarged single market. In the long term, EU enlargement will make the continent more prosperous.
Increased European prosperity is a net benefit to the United States. Given Europe’s preeminent status as a US trade and investment partner, its economic fortunes have particularly significant implications for America. A more economically dynamic Europe will create new opportunities for US exports and foreign investment, driving economic growth, job creation, and incomes. However, taking full advantage of these opportunities depends on the transatlantic partners retaining a commitment to economic openness — making it even more urgent for Washington and Brussels to avoid an all-out trade war.
A more economically dynamic Europe will create new opportunities for US exports and foreign investment, driving economic growth, job creation, and incomes
The case of Ukraine merits special attention. As the largest accession country — and with the United States now holding a significant economic stake in its mineral sector — Ukraine’s economic success would bring substantial benefits to Washington. But realising this potential will require a massive post-war reconstruction effort. Advancing Ukraine’s EU integration would support that effort by unlocking significant funding to help transform its economy.
A final benefit of EU enlargement for the United States is its potential to strengthen the European Union itself. While the Trump administration has often viewed Brussels more as a competitor than a partner, there remain critical challenges — such as countering the Axis of Upheaval formed by Russia, China, Iran, and North Korea — that demand transatlantic cooperation. Expanding its territory, economy, population, and defence industrial base would enhance the EU’s geopolitical weight. By supporting enlargement and once again treating the EU as its 'partner of first resort', Washington can amplify its own influence through renewed transatlantic alignment.
While the European Union revived the enlargement process following the 2022 full-scale invasion of Ukraine, momentum has notably slowed in the past year and a half. Following the highly symbolic December 2023 European Council decisions on enlargement, EU leaders are facing daunting obstacles blocking the path forward — including the need for reforms in both the European Union and potential new member states, along with unresolved conflicts and persistent vulnerabilities in accession countries.
Given its interests in successful enlargement, the United States should do all it can to help dismantle these barriers, operationalising a comprehensive strategy for advancing the enlargement process. Acknowledging enlargement as a US strategic necessity is an indispensable first step.
