If they're here to try to assess our air defense network, then a reasonable response is don't turn it on. Don't turn on the best radars. Don't turn on the data links from the air combat control centers to the air force bases (or to the planes in the air).
Sure, they can see the vanilla stuff better than they can from a satellite. But if the good stuff is off, they don't find out much about it.
> don't turn it on
There is no need to? It was detected long ago and was followed both with radio and visually.
If these spy drones and balloons exist, then you can sure bet they're doing something of value. Militaries don't design and fly these things for the fun of it.
And why are you assuming it's only a problem if they're better than us at it? We could be spying on them even more effectively, but that's not a reason to not prevent them from doing the same to us.
For all we know, China may have decided that every Baptist church is a possible nuclear launch site and that they all need to be priority #1 for surveillance. Particularly on Wednesday nights when all the folks in the surrounding community come in early in the evening and sometimes don't leave until late at night.
That's the stuff you don't get from LEO satellites.