The Russian invasion of Ukraine has exposed vulnerabilities in the Western liberal order, highlighting divisions in global security alliances, ideological conflicts, and defense preparedness. As the world shifts toward a multi-order reality, NATO faces the challenge of adapting to new threats and competing power structures while maintaining its strategic relevance. At the heart of these tensions is Donald Trump’s confrontational stance on NATO, which has tested the alliance’s unity. During his first term, he threatened to withdraw the U.S. from NATO, citing the disproportionate financial burden placed on America by European members failing to meet defense obligations. In the lead-up to his second term, he demanded members increase military spending to 5% of GDP, arguing that the U.S. has subsidized Europe’s security without adequate burden-sharing. This divide has deepened concerns over transatlantic security cooperation, with France advocating for a European army, favoring continental defense over Atlantic alignment. Despite diplomatic tensions and uneven military investment, NATO remains a critical pillar of Western security. Its ability to rebuild trust, enhance military readiness, and sustain unity will determine the future of global democratic stability and deterrence. In the broader context of Nation Against Nation, this chapter explores the erosion of U.S.-Europe relations, arguing that NATO must strengthen, not fragment, to withstand rising geopolitical volatility and protect its strategic foundations.