Brexit is in fact an example of how difficult it is to create a new nation from already pre-existing old nations

Add to this a lack of compromise from the EU, who think that the evident problems can be solved by faster, not slower unification. Then have a vote.

Actually you left out a couple of factors. First, a general feeling that Britain is paying for subsidies to free-loaders and not gettingback its dues proportion of the U budget, and second, a public perceptions that the mainland EU countries are deliberately failing to expel bogus asylum seekers and instead facilitating their efforts to smuggle them into Britain for our higher State benefits, while denying us the right to refuse those benefits.
Cheers, John