This article analyzes the United States and the People’s Republic of China as civilization-states shaping the emerging multipolar world order and global security architecture. Drawing on a civilizational approach, the study argues that the foreign policy behavior of both powers is rooted not only in material capabilities but also in deeply embedded historical, philosophical, and cultural foundations. The United States, as the leader of Western civilization, demonstrates patterns of expansionism, hegemonic stability, and competitive “zero-sum” logic, comparable to those of Ancient Rome. In contrast, China represents a continuous civilizational tradition emphasizing harmony, collectivism, soft power, and integration within existing international structures. The article examines official doctrines, strategic documents, and expert assessments from both sides to explain the growing strategic rivalry between Washington and Beijing. It concludes that current tensions stem primarily from divergent civilizational worldviews and security perceptions rather than from immediate hostile actions, making U.S.–China relations a key determinant of global stability in the new world order.