The urge to separate derives from centralized control of things better left to communities, towns, cities, cultures and nation states. In a global economy trade should be global, but there are few reasons to centralize most government policies, i.e. "public goods" When Europe or the US for that matter, was a customs union of internal free trade it grew prosperous and enjoyed peace. As it centralizes the cultural, ideological, and necessary governance give rise to conflict. The only reason to centralize was national defense and trade policy to defend free trade from local protectionist interests. As the centralized bureaucracy gathers power to itself, it threatens the thing that matters most, free markets and free trade.