Empires have existed for millennia, with imperialism encompassing the practices deployed in their creation, expansion and defense. The Twilight of American Imperialism describes the political, military, economic and cultural aspects of imperialism, and how these practices have been employed over the course of the 250-year rise, ascendance, and present decline of the American imperial project. Special attention is paid to identifying the distinctive characteristics particular to the American empire in its phase as dominant hegemon after the mid-20th century--as well as on the internal contradictions and external forces responsible for its emerging decline in the 21st. The Book predicts the likely trajectory of US imperialism over the next decade, 2025-2035, as it confronts intensifying challenges from the BRICS and the global south. The Twilight of American Imperialism enables a ready grasp of: - the major literature of theories of imperialism--Marxist, pro-capitalist and Heterodox to develop a common definition of the fundamental nature of Imperialism in its various dimensions. - the trajectory of American imperialism from its colonial origins, offshore expansion offshore from 1898 through World War II and thereafter from 1945 to the fall of the USSR in 1992 to the period of undisputed American hegemony up to the 2008 apex of American imperial power. - the institutional basis of American global empire after world war II: the $US, IMF, World Bank, SWIFT payments system, WTO, Free trade treaties, NATO and other military-political alliances, with special focus on the 'managed dollar' and 'twin deficits' systems. - the internal contradictions growing within the empire economically and politically since the 1980s and especially intensifying after the 2008-10 global economic crisis. - the numerous external forces developing in the 21st century challenging American global economic and political hegemony. - the US domestic indicators of corresponding social decline in America as a consequence of imperial expansion and decay. - the US wars of imperial defense in the 21st century, the rise of the global south economically and politically during the period, the BRICS intensifying challenge to the institutions of American imperial power, and the inevitable retreat and consolidation of remnants of the American empire on the horizon.