Brexit isn't prove of s*** because Britain itself is multi-cultural. This 'tribalistic' thing is bulls***. No one is born with a cultural identity. Even if you argue that it is ingrained in society, you are going to have a helluva time trying to nail down what exactly each culture is.
Let's take the British, for example. Okay, so first they were Celts who split off from the continental Celts and traveled to the British Isles in prehistoric times. Then, much later, those groups split (Picts, for example) into many different groups. Then you had the Romans show up and mix with them. Then you have the invasion of the Angles, the Saxons, and the Jutes (themselves three different 'tribes'). Then you have the invasion of the Danes, and the Danelaw. After that, you have the conquest of William the Bastard/Conqueror, who himself was from Normandy (and thus, French) and according to legend, descended from a Scandinavian (Rollo). Then you have the conquest of Ireland and Scotland, re-introducing those 'tribes'. Then you have the import of people from the various colonies (Canadians, Indians, Africans, Chinese, etc) all of which have a claim to being 'British' after several generations. So, what defines the British 'tribe', again?
To summarize, Britain is multi-cultural, and 'tribes' are not inherent ally to tribal to get along, because most of the current 'tribes' are actually mixes of tens, if not hundreds, of different cultures that amalgamated over time. There is no such thing as a 'pure' culture, and multiculturalism has been working longer than whatever the hell you are advocating.
A lot of that shit took hundreds of years to happen, and I know even within the UK, there is a ton of tribalism among different white groups. Scotland voted to stay... ---