Aren't you contradicting yourself?I mean, why not? unless China puts AA assets all along the coast what's stopping the US from lobbing cruise missiles using strategic bombers day in day out? After JASSM runs out, they still have older LO cruise missiles. You'll have b-52 parked mid way between Pearl harbor and japan lobbing cruise missiles all day every day, the barrier to US military missile procurement is political, not by inability. I doubt China has such a stockpile of AA missiles that they can intercept every single one of them, nor do I think that those AA assets are not better spent elsewhere. Like I'm not trying to disparage China here, they have a formidable military, but the US has 40 years of cold war spending to throw at a China sized problem and it's going to take some time for it to equalize.
First, you say JASSM can evade the air defenses deployed
Second, you say (more?) air defenses will need to be deployed
If the US is striking mainland China, what "elsewhere" is there to put these AD systems?
Russia has already exhausted a lot of NATO's stock of ATGMs, so why do you think China wouldn't be prepared to deal with US long range fire even with 40 years of stocks?