It would end up the same as today, ultimately, nations would emerge. Don't you think "free association" is where civilization began at first place? And you expect a different outcome? Who would protect "free associates" from the violence of others who don't buy into that system?
Utopia like Anarchy severely ignore the "human nature" factor.
It's unknown how civilisations began but they were most likely not formed through "free association" but rather by violent extortion. It's thought that pastoral communities being regularly robbed by nomadic groups eventually developed a relationship of paying tribute to one group in return for protection against others. Or, put differently, one group of bandits will fight off the others to get exclusive pillaging access to some farming communities. This tribute system is believed to have then developed into a taxation system.
In no way are modern nation states a form of "free association". I cannot freely choose to not pay taxes if I am born in a nation, nor can I freely choose to join another nation if I accept their principles.
Your predictable and very unoriginal use of the "human nature" argument is in fact the ignorant position. It completely ignores the significantly larger number of humans throughout history (and including today) that have lived in freely associating relationships that in no way resemble the modern nation state or earlier forms of civilisation.
You cannot find a single example of what you deem "free association" that is not currently defended directly or indirectly by an army.
The irony of your statement is that while you called me ignorant you said the exact same thing as I said in your first paragraph.
Then you try to back pedal to make a "point" in the last one by giving zero examples of your "larger number of humans throughout history (and including today) that have lived in freely associating relationships.
And next time refrain from calling other people who disagree with whatever ideology you believe in as "ignorant", it qualifies you as a troll.
Utopia like Anarchy severely ignore the "human nature" factor.