i think one of the best set of examples is probably provided by the united kingdom and its constituent parts.
the different portions of the kingdom were brought together with england by different means. the welsh by conquest. the scots by the act of union under james vi of scotland. the northern irish via the partition of ireland.
but once joined together, i think there has mostly been a majority in favour of not splitting asunder through the years, even if sometimes there has been some strain.
even so, the union remains a voluntary thing based upon the will of the peoples within each country. occasionally referenda are held to test the waters of change.
scotland is moving towards a democratic vote to see if it wishes to become independent. i think it is a simple majority thing, although usually there is a stipulation that a certain percentage of the electorate must vote if the thing is to pass.
this is also complicated by the fact that many scots live outside scotland. so is it only the scottish scots and various other resident categories or they and the expat scots who get to vote? i think it's only the former at present.
you are right to point to the sense of obligation from the centre to the different countries. northern ireland has not been a bed of roses. but the rest of the uk perceived an obligation towards those who wished to remain a part of the uk during the troubles. and in fact, contrary to much american reporting, those people have always been the majority! now it is mostly a self-governing country within the uk, with a bit of an advisory arrangement between eire and the uk for the bits that aren't.
whereas wales has always had a majority in favour of remaining inside the uk. it has its own assembly, just as scotland does. but the big decisions are taken in westminster.
one last point. the argument was made that everyone in the uk should be permitted to vote on scotland's independence - the argument being that everyone is affected by it.
answer was no.
the scottish independence movement has been slow. i think that is the right speed for it. i don't know if many people resent the fact they wish to govern themselves. or feel the need to preserve a union in which one country no longer wishes to remain. i don't.
it is a helluva lot better to let folks go than fight to force them to stay. at least once they see themselves as having a divergent set of loyalties. much more likely that the relationship will be friendly and indeed, that perhaps they will change their minds at some point when the english rebuild hadrian's wall to keep the scots in scotland. ;-)
i see the same possible roadmap for the usa as the red states and the blue states keep falling further apart.
but maybe the gop will transform its political philosophy so that it is no longer quite so divisive and so determined to make washington ungovernable. to me, that is an unsustainable status quo.
as you probably know, i've been thinking this for some time. i am impressed how few folks will consider it. i guess this is because the reservoir of patriotism to the usa is very deep. and that is a positive thing on the other side of the debate.