The analysis presented in this thesis focuses on the evolution and resilience of American power over Europe in the aftermath of Russia’s full-scale invasion of Ukraine in February 2022 while clarifying the conceptual framework of power based on the distinction among hard, soft and smart power. The historical overview revolves around the progression of American prominence throughout Europe during the period 1991 - 2021, the phases of unipolar dominance, the tensions following September 11, the rupture after the five-day war in Georgia and the events in Crimea towards drawing conclusions with regard to the extent of US supremacy’s maintenance and Europe's growing capabilities. Methodologically, the thesis is structured upon a literature review derived from academic research, official NATO and EU documents, US governmental reports, analyses and intergovernmental texts while it refers to the period between 1991 and 2025 with particular emphasis on the post-2022 sequence of incidents. According to the thesis’ conclusions, American power in Europe is not in decline but under reformation since the US retains its internationally leading role based to a large extent on the exertion of hard power, such as ISR, command and control, missile defense and nuclear deterrence with its institutional influence within NATO remaining pivotal. Nevertheless, political control appears to be increasingly conditional and subject to negotiation and legitimacy with European actors requiring more extensive autonomy on economic and diplomatic issues. Thus, the current war between Russia and Ukraine reveals a transition from US’s former unchallenged hegemony to a reformed state of supremacy within which even though American leadership is retained it has to be constantly reaffirmed.