How a West Coast attack could immobilize American sea power

Could a significant Japanese strike on the American West Coast have restrained the US Navy for months?

Yes; it could have tied a large fleet to coastal defense well beyond the immediate aftermath of the attack.

A significant Japanese attack on the West Coast would have triggered a major effort to secure the coast and protect it from a repeat strike. Ships retained for home defense could remain unavailable for offensive operations for much of the war. Japan's own reluctance to release important battleships from defensive roles illustrates the same burden. Even a limited attack can change force allocation by making political leaders defend a newly demonstrated vulnerability.