Numbers game, what's the maximum number of targets that can be covered in a window, the cost of dealing with non torpedo launch capable platforms is the same as the cost of taking out an actual torpedo carrying launcher - the overwhelming threshold is something that is tested in games, of course.

> If we're postulating magical "ai" attack drones loitering off the coast

I'm not, I'm looking at a reasonable near term extrapolation of what China already has and tested.

> what's stopping the americans from sending in their own fleet of equally magical ai attack drones to blow up all the defenders

The usual constraints of hunting and finding in vast area

> Also, again, you'd have to know exactly where the carriers even are

Well, approximately .. and that's what China provides to Iran via sat coverage.

> right now $80m worth of torpedo drones would cover like .01% of china's coastal waters.

I thought the carriers were off Iran and staged well back? I can't see them being as far back as China myself, but perhaps you have some curious reason for wanting to spread them out some place far far away from the conflict. I have no knowledge of that, obviously.