In "The Return of Marco Polo's World," Robert D. Kaplan asserts that while the European Union remains a significant entity, the rise of individual states, regions, and city-states indicates a precarious balance for liberalism against burgeoning populist nationalism. This fragmentation suggests that traditional alliances may be at risk, with national sentiments often overriding collective European ideals.

Kaplan emphasizes that underestimating the impact of these nationalist movements on NATO's cohesion is misguided. As populism gains traction, it poses significant challenges to the unity and effectiveness of NATO, highlighting the need for a reevaluation of strategies within the alliance amidst shifting geopolitical dynamics.