...snip...
Worked pretty good in medieval Iceland, for about 600 years, until an outside power bought up the judges. 1000 years in Ireland, before Cromwell finally beat 'em.
Surely that is all you need to know? If outside powers or hostile races like the English exist, then you need a state.
No, it means we need some way of coordinating defense. A state is one option, but I don't think it's the best one. And it took
centuries of attempted conquest before one finally stuck.