Except we have no problem with such diverse policy in other federations like the eu.
Frankly we're heading down the path of membership flexibility if the next few years don't bring about significant change.
It's not like the confederacy was fighting for slavery and to be part of the union. Both Kentucky and Delaware were happy with the status quo. The confederacy wanted both slavery and to leave the union, which they perceived to be their right.
The federal government at the time was much smaller than the current one and much less empowered.
The union stopped being good enough for them, when it stopped being perfect.
You'd be hard pressed to argue the confederacy wanted to take over the union and then impose slavery on the free states. I mean, you could make the argument, but it's more likely to me they simply wanted to leave and continue enslaving people.
I don't know how this turned into a discussion on slavery. The issue was secession. The civil war answered that us states cannot secede. Itll be interesting to see how the dynamic in the eu changes since this is a possibility there (although I'm doubtful they'd let a continental member leave).
I can't see its use being refused: that would disintegrate the bloc. And there was no question that we (the Brits) wouldn't be allowed to, so the precedent has been set.
I would imagine a few tweaks to the Article 50 exit mechanism will be made next time the treaties are revised - there are some game theory problems in the current trigger mechanism and the timescales set down turned out to be too short in practice - but it's no longer in dispute on principle.
It was also not in dispute in the first constitution of the united states, but they just did away with that for funsies (I'm being facetious). I imagine we'll see something similar in the EU as the bloc becomes more integrated.
In the past, if you traveled from San Francisco to new Orleans you would experience an entirely different set of stores, a new dialect, new customs, and frankly a new language.
Even the difference between California and Oregon is stark. California being mainly Hispanic and Oregon being mainly Nordic and with lots of Slavic influence. The names change and even the languages do.
I'd never see Russian in California but it's a regular occurrence in Oregon.
EDIT: By no means am I suggesting though that Americans do not have fondness for one another. I just think the relationship between a rural Alabaman and an urban Californian is more like the relationship between two citizens of differing EU countries. We certainly have a shared culture of sorts, and we will defend each other in the face of non-Americans, but there are cultural differences that cannot be simply glossed over.