The new US national security strategy marks a significant historical turn. It shifts the focus from global overpopulation to anxieties around population decline in the western world. Coupled with renewed criticism of Europe’s military weaknesses, the strategy updates longstanding anti-European narratives.US-European relations have so profoundly influenced the course of the 20th and 21st centuries that New York University historian Mary Nolan refers to this era as the “transatlantic century”. The relationship revolved around military interventions and consumer cultures. American involvement was decisive in both world wars and in the European wars following the breakup of Yugoslavia. Europe also emerged as a crucial area for the expansion of American consumerism and market norms. On both sides of the Atlantic, the interplay between military interventions and market cultures shaped not only cooperation but also mutual resentment. In Europe, as early as 1902, people were beginning to express anti-American sentiments which were often centred on fears of cultural domination. Later, British bands such as the Clash and the German band Rammstein amplified these perceptions in popular culture, with songs such as I’m So Bored with the U.S.A. (the Clash) and Amerika (Rammstein). The Clash: I’m So Bored with the U.S.A. In turn, anti-European ideas in the US centred on perceived European military weakness – a critique with some historical evidence to support it. The lend-lease agreements supplied the UK and the Soviet Union with desperately needed military aid. Without it, neither country would have been able to sustain their war efforts against the Nazi advance in Europe.After the cold war, Americans expected Europeans to assume a greater share of global security responsibilities. But, in two major cases, Europe fell short of these expectations. During the internationally coordinated intervention against Iraq’s invasion of Kuwait in 1991, the US contributed more than half a million troops. The UK, France, and Italy together only contributed 93,000.Germany supported the military campaign only financially. This imbalance prompted US commentator Charles Krauthammer to label the US “the lonely superpower”.At the end of the 1990s, the Nato-led bombing campaign against Serbia was likewise carried largely by the US. US aircraft conducted 70% of strike missions and 90% of defence missions. Without American intelligence support, meanwhile, the campaign would have faltered. As one leading German diplomat admitted: “Kosovo was two or three sizes too big for us.” The Iraq war in 2003 reinforced US perceptions of European weakness. Countries like Germany and France did not support the war and, in the language of the hawkish American right, these countries were cast as emasculated and mocked as “Euroweenies” and “EU-nuchs”. US defence secretary Donald Rumsfeld, a leading advocate of the war, was celebrated as a hyper-masculine “stud”.It is a striking twist that today’s “America first” conservatives embrace the critique of the Iraq intervention that had been aired in Europe. It is, they say, not their war. But Europe’s continued dependence on the US, particularly in its support to Ukraine, appears to confirm perceptions of military weakness. Population enters the debateAnti-European sentiments related to military interventions have a long history. Now, concerns about Europe’s native population decline represent a new element of the US national security strategy.In modern history, population trends have consistently generated anxiety. They ranged from Malthusian fears of food shortages in the late 18th century to 20th-century worries about global overpopulation. As I show in my own research, Europe and American thinkers were key in shaping this debate. Advocates of population control on both sides of the Atlantic coordinated campaigns to reduce global fertility rates, particularly in developing countries.Overpopulation arguments still simmer. But it has recently been overshadowed by a major shift towards concerns about population decline.Elon Musk has become the American embodiment of this trend. Not only did he father many children but turned demographic decline into a political cause. He has argued that a “collapsing birth rate is the biggest danger civilization faces by far”. There are concerns about the declining fertility rate in Europe. Eruostat In Europe, this position is embraced by populist anti-immigration parties. Their resentments resonate because they tap into real demographic trends. Between 1990 and 2020, central and eastern Europe’s population fell by 8%. The sharpest declines were experienced by some of the poorest countries, among them, Bulgaria – where population fell by 24% – and Romania – where it fell by 17%.Populist rightwing parties in the US and in Europe advocate boosting native birth rates. They present this as an alternative to a perceived western European model that relies on immigration to sustain welfare states. In their 2020 study for the Journal of Democracy, sociologist Ivan Krastev and legal expert Stephen Holmes note that the “preoccupation with demographic collapse … manifests as a fear that the arrival of unassimilable foreigners will dilute national identities and weaken national cohesion”. The speeches of leading rightwing populists, including Hungary’s prime minister, Victor Orban, and Serbia’s president, Aleksandar Vučić, vividly illustrate this worldview. Orban insists that, contrary to western Europe, “we Hungarians have a different way of thinking. Instead of just numbers, we want Hungarian children. Migration for us is surrender.” Vučić similarly warns that without a demographic turnaround, Serbians “will stand small chances to speak about our own survival in the territory of the rest of Serbia”. Comparable sentiments are echoed by western European anti-immigration parties, including Germany’s AfD or France’s Rassemblement National and became a major feature of Trump’s presidency.Overall, the new US national security strategy marks the culmination of a wider realignment in which the conservative right on both sides of the Atlantic has rallied around demographic decline as a central political concern. This perceived decline now constitutes a central pillar of US national security thinking. For Europe, meanwhile, Washington’s attempts to bolster European rightwing parties may themselves become a source of instability and polarisation in the years to come.Roman Birke does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.