This comprehensive ECPS report examines how the resurgence of right-wing populism—most notably under Donald Trump’s second presidency—reshapes the foundations of EU–US relations. Bringing together leading scholars, the report analyses the erosion of trust and shared norms across four pillars of the Atlantic order: security, trade, international institutions, and democratic values. It shows how domestic polarisation and illiberal trends now pose deeper, longer-term challenges than traditional diplomatic disputes. Combining theoretical insight with concrete policy recommendations, the volume outlines how the European Union can adapt strategically to a more volatile partner while defending multilateralism, democratic principles, and European strategic autonomy. An essential resource for scholars, policymakers, and practitioners navigating a changing transatlantic landscape.