That depends on the state, many states are default open to travel in open land and require posting / signage to block free access. Pretty much all trespassing laws require notice first (of which adequate signage counts as notice) and you are not trespassing until you have been told to leave and don't.

Sounds like yet another interesting survival challenge.

Having been homeless and stealth camped extensively I can assure anyone reading that with no car and greater than .25 mi from a road or home you are invisible to 99.99% of population and 100% of local cops. The only guy that ever found me out was a forest ranger who wildly I randomly met on foot several miles away from nearest road in rugged terrain (and that was way too far for him to mess with hauling me to jail).

In my long career of first hitchhiking the world and then bicycle-touring/bikepacking it, I have spent hundreds of nights outside stealth camping, but I have been caught more often than you suggest happens. Farmers in some places do daily rides around their land to check for squatters or illegal tree-felling. Male friends so often like to walk into the woods and drink (and fire off weapons, which can be unnerving to one sleeping). And I’ve been told by forest rangers that they are increasingly using drones to surveil forests instead of having to go down every trail themselves.

Interesting. Your experience is wildly different than mine, although i admit I always restricted stealth camping to at night with a bivy the same color as the terrain and I have a pretty good sixth sense of good cover. I would have definitely avoided areas worn enough to suggest daily ride around or worn enough to be the no-thought default path of a drunk, which probably shielded me largely from your noted encounters.