Noah Caldwell, writing at American Renaissance, gives a good first person account about why he believes, from his experience, multicultural societies do not work. What he says is equally, if not more applicable to Europe: “I have long lost track of the number of people I have encountered who barely speak functional English yet hold an American passport. They and the illegals who flood this country daily bring with them their loyalties to the country of their birth, their religions, their values, their genetic proclivities — a potent combination which more times than not is at irreconcilable odds with the foundational tenets of European civilization. It is no secret to those who study history that like all empires that have come before, America as we know it has entered its final throes. The barbarians are no longer at the gates. They are among us.”
And, it will be as in ancient Rome for a people who never learn the lessons of history.