How long after the Chinese sank one would it take before their entire fleet was a reef?
Weeks, if ever.
We don't have the resources we once did. And, arguably, they are ahead of us in certain high altitude weapons technology. Unless the X-37 has capabilities we are not aware of, it would take us time to track down their entire fleet.
Now, if they were to sink one of ours, their carrier would sink within a few days, I suspect. They've got 50+ submarines, and probably double that in pretty big boats. (That's not intended to be a technical class of warship, just an attempt to capture the ships that could cause us trouble.)
Its a big ocean.