Purpose This study aims to investigate the decline of American hegemony as one of the most prominent crises of the modern world order, from a broader perspective that transcends narrow traditional interpretations. The paper assumes that the September 11 events in 2001 have launched the actual decline in American hegemony. Tracing the evolution of US global strategy over the past two decades, the study seeks to analyze the main causes and repercussions of the decline of US hegemony, which would provide a bird’s eye view of what the current global system is going through. Design/methodology/approach The study investigates the decline in American hegemony through a longitudinal within-case analysis which focuses on the causal path of decline in hegemony in the case of the USA, since the events of September 11, 2001, and tries to identify the causal mechanisms behind this decline. Following George and Bennet (2005), the study uses process tracing to examine its research question. Process-tracing method seeks to identify the intervening causal process – causal chain or causal mechanisms or the steps in a causal process – that leads to the outcome of a particular case in a specific historical context (Mahoney, 2000; Bennet and Elman, 2006). The study chose this method, as it offers more potential for identifying causal mechanisms and theory testing (George and Bennet, 2005); it opted for a specific procedure, among the variety of process-tracing procedures listed by George and Bennet, which is the detailed narrative presented as a chronicle, accompanied by explicit causal hypotheses. Using this process tracing procedure, the study assumes that American hegemony has witnessed dramatic changes in the aftermath of critical junctures, particularly the events of September 11, 2001, and the financial crises, 2008, which contributed significantly to this decline. Consequently, it traces the impact of these events on the state of American hegemony, in light of the review of contributions of different theories on hegemony in the field of international relations, both traditional and critical. Consequently, introducing the theoretical framework used in the study (the four-dimensional model of hegemony), which transcends criticisms of previous theories. Findings The crises of the modern world order and the decline of American hegemony – being the main manifestation of such crises – revealed the inability of the traditional and critical approaches reviewed in the study to interpret this decline and those crises. The reason behind that was the inability of these interpretations to reflect the various dimensions of American hegemony and its decline since the September 11 events. This highlights the importance of using the four-dimensional model, which combines different factors in the analysis and has proved to be an appropriate model for studying the case of American hegemony and its decline after the events of September 11, as it deals with the phenomenon of hegemony as a social relationship based on specific social networks. Originality/value Despite the currency and relevance of the decline of US hegemony for both the academic and political world, the topic needed to be analyzed systemically and addressed in a thorough scientific way. Through the application of theoretical concepts into the analysis of empirical data, this study contributes to a field where too often the discourse about decline of American hegemony is led without the required theoretical or conceptual considerations.