Absent mass automated surveillance, the state's ability to do so at scale was limited.

Once implemented (and processed and stored), norms on use erode over time... and then anyone anomalous is being auto background-checked when showing up in a new area.

Or do we think someone won't find a use for all the dark datacenter GPU power after AI pops?

That is the historical norm. Is it supposed to be a new concept?

Even the most closed societies (say, East Germany, the USSR, and the DPRK) only accomplished a fraction of what's now technically possible, and that historical analogue through a massive human labor force.

The norm is that you're born somewhere and you stay there forever. Everyone there knows you and they've known you since you, or they, were born. If a traveler happens to show up, everyone can recognize immediately, by looking at their face, that they're from somewhere else. Strangers get low levels of trust.