This book investigates the hegemony of the USA by examining the Obama, Trump and Biden administrations’ responses to major global crises. Combining a Gramscian framework with the main features of complexity theory it provides a comprehensive account of the systemic crisis of the hegemonic order of the United States in security, environmental, and economic issue-areas. By examining key case studies, the author reveals that the hegemonic responses of the US were confronted by overt challenges, including emerging state and non-state actors, globally complex transnational flows, and a combative domestic political climate which undermined the United States’ role in multilateral institutions no longer fit for purpose. This book will be of interest to general readers as well as scholars and students of US foreign policy, global politics, and Gramscian theory.