It has been a commonplace of liberal, and in particular democratic, political rhetoric that government rests solely upon the consent of the governed. The logical conclusion of this principle, of course, is that every single individual ought to be able to determine the exact nature of the polity in which they choose to live. This is of course an utterly unachievable goal, but it is worth considering how far we can move in that direction - and whether such moves are likely to be desirable.
So far, the closest we have come to achieving this kind of choice is to allow for collective decision-making about how governance should take place. This is, however, a pale shadow of the ideal we are aiming for: collective choice may reflect the preferences of all in a group of four or five friends, but in a nation of thousands - let alone millions, or even hundreds of millions - the individual voice is a mere drop in the ocean.
Another possible way to move in the direction of individual consent is to institute a variety of polities, and allow free movement between these. There are still problems with this system (call it "Archipelago"), both in terms of individual choice and in terms of the practical problems it throws up, but it remains perhaps the closest to utopia we are ever likely to reach. I'm not going to defend it here, but section III of the linked article provides one person's attempts to expose and subsequently resolve the problems with it. As I see it, the principal differences between Archipelago and one inhabited by modern-day Europeans are few but highly significant. These differences can be bridged, but would require substantial, and highly controversial, changes to the current political set-up.
A first difference lies in the vast legal and logistical difficulties faced by anyone attempting to move from one polity to another. The EU has done a considerable amount to reduce the legal barriers, but there are nevertheless very considerable costs to moving. There are the large financial costs, the friends and family with whom you have considerably less contact, the difficulties of learning a new language (or reduced quality of life if you don't learn it), as well as all the frictional costs of adapting to a new set of cultural institutions. Some of these costs are unavoidable, but others could, I think, be much reduced.
The key step to be made here is the abolition of the nation-state. Or rather, the splitting of nations into several different states. The costs of moving from Aldershot to Bath are much smaller than the costs of moving from Austria to Belgium, and that would continue to be the case if Hampshire and Somerset were separate states. It is true that political differences can lead to cultural differences which magnify over time, but the fact remains that after more than 200 years of independence the USA remains the number-two destination for British emigrants - topped only by another former British colony, Australia. In terms of the existing stock of British expats, five of the top six destinations are Australia, the USA, Canada, the Republic of Ireland, and New Zealand. Splitting the UK into anywhere between a dozen and twenty smaller states would allow Brits a real choice of political entities in which to abide.
The second, and perhaps the biggest, difference between Archipelago and the real world is that real world states really aren't all that different from one another. There are differences, but you'll struggle to find a single first-world economy that has anything other than a welfare-state vaguely-capitalist mixed economy. Switzerland has genuine variation between its cantons, with some places such as Zug levying almost no taxes whereas Geneva will tax anything you can shake a stick at, but they are entirely the exception (and of course anyone wishing to move into Switzerland from the outside faces some of the strictest borders in Europe). Achieving Archipelago means being willing to see people recreate communism, fail, and ruin decades of their lives. It means being willing to see first-world countries where women are not allowed to vote and where homosexuals leave as soon as they can. Above all, it means trusting that there will be states like Estonia who try new, exciting and above all good ideas, who will lead the way for everyone else to follow.