1) Double the sub fleet (this will take years).
2) Deploy them to the Pacific Command
The sub fleet was "doubled". The US used to have lots of attacks and boomers. Go to the ship rolls and see how many subs have been removed from service, especially during the 90's.
It takes a lot of money, sailors, and nucs to maintain a large sub force. The threat from large formations of Soviet ships had gone.
The US is sending lots of money to China and doesn't have the money for the large fleet anymore. 500 billion dollar deficits, health care that guarantees a cat scan for every American and undocumented immigrant and their pets, and lots of porks for congress people kind of takes money away from the large fleet.