Big assumption: US/Japanese counterattack.
Japanese counterattack? Sure.
The Japanese aren’t stupid. If they aren’t ready for this, shame on them. I know how they feel about being Japanese, and about their homeland.
They may love the ‘Pease Constitution’, but they don’t live in windowless rooms. These folks live in a society that accepts that plans are made 100 years out. Families sign 100 year mortgages.
If you’re China, you’d better be ready. A single carrier isn’t going to get the job done either. Chinese amphibious capability is still not what it needs to be get it done either.
Would Japan use a nuke? Why not? It worked on them. Nobody adapts to new methods, techniques, and technologies more pridelessly than the Japanese. Any new idea, no matter where it comes from, is something they’ll adopt.
Japan has nuclear weapons?