What's at stake here is more fundamental than federalism: it's self determination. Throughout history, discrete groups have waged wars of independence to ensure that they can have a government that reflects their shared history, culture, and values. My family is from Bangladesh, which fought a war to separate from Pakistan over cultural/linguistic differences. In another example, Israel is engaged in an existential battle to ensure the existence of a sovereign nation for its people.

In Europe, exactly the opposite is happening. People are being prodded to give up their sovereignty to a supra-national bureaucracy, and to be assimilated into a hetrogenous body politic with hundreds of millions of other people with which they share little other than said bureaucracy. People in the U.K. were very rightfully afraid of what that could lead to and decided they wanted to get off that train.