Reflections on international relations after the end of the bipolar era have been dominated by visions, theories, and narratives that interpret the developments and perspectives of world politics in varying, sometimes opposite ways. The very position of the United States in the global era has always been the object of often radically diverging assessments. This essay reviews the debate on this specific topic. It starts with Paul Kennedy's' well-known theory from the latter 1980s and then attempts to follow the essential turning points in a debate that has set up two opposing schools of thought. On the one hand, there are those who hold that the Unites States is a solidly or almost solidly dominating power that is unrivaled in an essentially unipolar world. On the other hand, there are those who hold that the United States is in decline, at a turning point, and even at a point of immanent twilight within the context of a return to the more traditional dynamics of multipolarism.