If something like this macroagent actually existed, any time the macroagent faced a decision it had to make globally for one reason or another, it would make that decision in a way that reflected the preferences of everybody inside it. "Nobody anywhere gets to run a city where some children don't get to learn Baseline, even for the noblest possible purposes of scientific experimentation to see what happens if you raise kids speaking only your new improved language instead" - this is a decision made over everywhere; if there's any loophole somewhere, something will happen that most people in Civilization think should not happen anywhere.
(This example, to be clear, was selected on the basis of its controversy; propositions like "all children get to learn some human language during their critical maturation period" pass with much higher supermajorities. "Children don't have imaginary-ownership-tags pointing to their parents", goes the proverb out of dath ilan; there are limits to what Civilization thinks a guardianship-tag on a child should allow a parent to do.)
The system of imaginary ownership-tags, likewise by its nature, is something that needs at least some global structure. It can potentially divide into compartments that fit sub-social-systems, say where a family is tracking who owns what in an informal way that property-registers don't track. But there's not much reliability in owning the food in your refrigerator, if anybody anywhere in dath ilan isn't part of the system and can come in and eat your food in a way the police will shrug and not do anything about.
There is, at the top level, one system of private property. Weird experimental cities that are trying something else still, in the eyes of the rest of Civilization, have all the stuff inside them tagged as belonging to a persistent-contract representing that city; the rest of Civilization will then not come in and eat their food unless the city's persistent-contract says they can.