At the end of the Fifteenth Century, Europe began its colonization of the world. A few centuries later, nearly every part of the world had fallen under the sway of Spain, England, France, and the Netherlands. These empires eventually crumbled, the last of them in the second half of the twentieth century, but the world had been transformed. North America, Australia, and New Zealand were irrevocably Anglicized. South and Central America were Latinized. Africa too, was utterly transformed. Only the Ancient civilizations of the Near and Far East retained much cultural integrity. I would argue that even that is largely illusory.
Cultures, like any evolutionary product, resist destruction and replacement. After all, they would never have emerged or endured without some self-preserving traits. When the European empires fell, the newly independent nations rushed to reclaim their respective cultural heritages. For the nations where the indigenous cultures had been most thoroughly extirpated, this wasn't really a problem, but elsewhere it was. Colonialism had disturbed the power relations, especially where one empire had replaced others.
Its legacy, very often, was internecine slaughter and national fragmentation. India is perhaps the most interesting case. Various empires, both internal and external, have tried to unify that diverse civilization, but the British had the most recent and long term success. In doing so, they replaced the Moghuls, a dominant Islamic empire ruling a majority Hindu culture. I imagine that the Muslims did not appreciate that, but the end of British rule brought another threat, submergence into and domination by the majority Hindu culture. Muhammad Ali Jinnah focussed these fears, and aided by British ambivalence about a united and independent India, brought about the creation of Pakistan.
Roosevelt, and internationally minded Americans in general, thought this was a terrible idea, and history has not done much to indicate that they were wrong. Separation of populations by religion was never practical, and attempts in that direction have led to terrible carnage. Pakistan itself has since fragmented into two countries, and Pakistan has remained an economic failure.
This is the starting point of MAGNIFICENT DELUSIONS: Pakistan, the United States, and an Epic History of Misunderstanding by Husain Haqqani, former Pakistani Ambassador to the United States.
Haqqani, Husain (2013-11-05). Magnificent Delusions: Pakistan, the United States, and an Epic History of Misunderstanding . PublicAffairs. Kindle Edition.