Although I doubt there is any US Navy weapon designed to obliterate a target sitting on the bottom.

It might be difficult, however. For example, anti-submarine weapons are designed to locate and severely disable or damage a maneuvering submersible. I can't think of anything (short of a nuke) that can eliminate every single chip and integrated circuit, or stealth composites.

Surely the Navy can figure something out, but probably not before a rival could locate and retrieve the wreckage. Probably the best weapon would be an old-fashioned WWII depth charge, lowered on top of the wreckage and remotely detonated. But I can't think of anything in the arsenal today which could do that. Depth charges today are designed to be delivered by missile and parachute to targets many miles away. I don't know if they could be adapted to go after this wreck. And of course, locating it is something else alltogether. Although there are deep spots in the S China Sea, much of it is really shallow.

Here is an example of a nuke depth charge...

My ship in the Navy was equipped with an ASROC (Anti-Submarine Rocket) battery with 8 missiles, including both depth charges and homing torpedoes. But it was the most secret weapon we had aboard. I knew absolutely nothing about it. It was never fired while I was aboard.