A bunch of people doing whatever the fuck they want doesn't seem like it would result in a lasting country of any size.
Sure, when you phrase it like that. But actions will still have natural consequences, and (smart) people are going to consider that when they make their voluntary decisions.
For an extreme example, if I go around saying that 9/11 was a good thing, people are going to avoid me, at best. Depending on how vocal I was, I could have trouble finding a job, businesses and other institutions with a reputation to keep would ban me if they felt it was necessary, and if I was really vocal, I could even be a threat to the property values of wherever I live, forcing me into a shitty neighborhood.
Sure, it's not a good thing, and it is technically possible in a Voluntary society. But that's exactly why if, for no other reason (such as empathy or a lack of insanity), people agree 9/11 was bad. They're disincentivized from rejecting cohesion to that extent because it would make them outcasts.
But the bottom line is that it's more important for them to have a choice than it is for them to think 9/11 was bad. Let them dig their own graves if they wish.
I could even be a threat to the property values of wherever I live, forcing me into a shitty neighborhood.
Unless you own your home, and if society can't force you off the land then you are now damaging your neighbors' property (value).
(not that I think society should be able to force out a property owner, but it does create a minor paradox)
Can you define cohesive?
Without knowing what you mean, the best answer I can give you is that it wouldn't necessarily remain cohesive, but it wouldn't necessarily not either. It depends on the density of people who would naturally behave this way in your society. But they must do it voluntarily, of their own will.
Is it something you think people truly can't do without being forced to by an involuntary state? Could a voluntary state or institution of some kind not incentivize people to behave this way by choice?
If so, is cohesiveness really so valuable that you must threaten people with violence to comply with it? Would you be willing to enforce this yourself, by arresting people who don't comply, and even physically harming or killing people who resist arrest?