Most empires have vanished into the pages of history books after they were captured by their former vassals or colonies.
The Persian Empire was captured by its former vassals, the Macedonians (led by Alexander the Great). The Roman Empire was captured by its former vassals, a coalition of Central Asian and European barbarian tribes led by the Visigoths. The last traces of the Byzantine Empire were captured by the Ottomans, who were once the vassals of the Byzantine Emperors. The Arab movements, which ruled Southwestern Europe (the Iberian Peninsula—Spain and Portugal) for almost six hundred years (711 to 1492), were initially being supported by the Byzantine Emperors and the political establishment in Italy. The Zangid Empire was replaced by Saladin’s Ayyubid dynasty (the Zangid ruler Nor ad-Din was responsible for the rise of Saladin). Ayyubid dynasty was replaced by the forces led by their former slaves, the Mamluks, who established the powerful Mamluk dynasty. The Mongol Empire was captured by the powers that arose in their former colonies of Russia and China. The Ottoman Empire was dismembered, between the eighteenth and twentieth centuries, by a series of coalitions in which its former vassals and colonies played an outsized role.
If this trend of history holds in our time, then the American Empire, which has been dominating the world after 1945, could be captured by political forces dominated by the people of South American, African, and Middle Eastern origin. The European colonial powers—Spain, Britain, France, Germany, and Italy—could be captured by the forces from North and South Africa, the Middle East, China, Russia, and even South Asia. These transformations in world power are likely to happen in the next 50 years. Already we are seeing the trend of the people of non-European origin (whose ancestral roots lie in the former colonies) playing an outsized role in the local and national politics of most Western countries. The legacy of imperialism will come to an end when the colonial powers get colonized by the people from the colonies.