If decentralized societies consistently require centralized allies to survive against centralized opponents
That's not what I meant.
They don't require centralized allies, nor do they necessarily require strategic allies at all depending on the circumstances.
The point I was making was if the US had undergone a Catalonia style anarchist revolution nationwide in the 1930's, It then would've been able to render aid to Catalonia, which had much less productive capacity pre-revolution, and thus could not out-logistic the 4-on-1 battle they faced. As an aside, an Anarchist US would not be dependent upon outside help to defend itself militarily from Mexico or Canada, had they wished to intervene. Nor would any other nation have been able to interfere due to the logistics of landing an invasion force and holding all that territory, or competing against the industrial capacity of the US.
I was also pointing out that in the specific scenarios where this style of organization was attempted but destroyed, they were destroyed due to their specific circumstances, not due to any aspects of it being decentralized. You appear unfamiliar with the details of both the Spanish Civil War and the Ukrainian Black Army which would make that apparent, otherwise you would not be making such blanket statements.
It would be like if I pointed to Germany losing in WWI or France quickly falling at the start of WWII purely due to both having a centralized governments. That would be an absurd statement because each lost for a multitude of reasons including logistics, war fatigue, tactics, the specific defense treaties they had signed before hand, etc.
Mutual aid works great inside trusted networks
What research are you referencing when making that statement? What is or is not a trusted network?
Even if we solved basic food and housing, scarcity doesn’t disappear. Water rights, strategic land, energy infrastructure, and transportation networks still create conflicts between groups.
If there were large Anarchist territories, the places with abundance could transfer that excess to the places that need it, or people could easily move away from places with scarce resources to places with them, as they would not be land-locked to their particular area due to poverty. A large mutual aid network really does solve the problem of scarcity. If you want to see that depicted in a very realistic and sensible matter, I implore you to read The Dispossessed by Ursula LeGuin.
I’m not saying decentralized governance can’t work or that councils are a bad idea. Local governance often works better than distant centralized control. I’m just skeptical that a system made entirely of federated local councils can scale indefinitely without recreating the same coordination structures states developed.
I don't mean this as an insult or to demean you in any way, but I think that without you personally wanting to do more research into this area to go beyond the surface level idea or theory, you will likely always remain skeptical of it regardless of its efficacy. This is a natural response, as you're already quite familiar with how our current systems operate, and they're quite old, so they seem quite viable just by their very nature of being the current default.
I've proved some research material in my previous comments, and I could provide more if you're interested, but ultimately I don't think any of my arguments will be terribly convincing without the real-world context to back it up, which is out there, but I realistically cannot provide all of that in a comment chain.