Tribalism has been in place for thousands of years. It is part of the human DNA. Any theology or governmental system that tries to change human behavior is destined to fail. Diversity is not a strength nor is multiculturalism. The elites may try to impose it, but there will always be resistance.
It sure is. The globalists know this well. The historical civilizations have to die, or at least their number reduced. Western Civ. (or at least its liberal leadership, and by "liberals" I mean all of the power brokers, of all parties) is in the process of committing suicide.
The predicted "death" of Western Civilization is premature.
The globalists will accommodate the tribal instinct. No sweat. They can have the Islam branch, the Eastern branch, and the Western branch, with each branch having its own customs, and roughly its own territories; and each branch seeing the others as co-equals, under a common world government.
There has been an incredible rise in the power of world institutions in the last 100 years. As with everything, ups and downs. Brexit and Trump are "downs" for the globalists, but the globalists will never be out.