Scenario wise for the PRC it would be units preloaded on container ships and commercial aircraft which would make a play to seize the coastal port/airfield and military facilities.
The SF Bay Area would probably be the easiest ones to seize followed by Seattle and L.A. (but a bitch to hold with 2 CVG groups offshore). If those facilities were taken, even temporarily, it would seriously impair service and resupply of Pacific assets.
Airports here would probably be the easy part. Couple airliners each with troops inside and gear as luggage.
Average Joe patriot would probably play a critical role here, harassing and holding up movement until organized units of the armed forces could respond.
As a surprise this would be a serious threat, but with all the movement and activity going on the probability of success is greatly diminished unless there are serious quantities of sleepers and northern/southern border area support covertly inserted also
Getting here is one thing having your resupply get here another as is no air support and unfriendly residents. China doesn’t have the resources to project power to Taiwan let alone here. After this is over they will have even less as the coalitions against their aggression coalesce.
If you like your Three Gorges Dam, you can keep your Three Gorges Dam.