GK - Thanks for the not wholly accurate slur, confirming LO's First Precept that in any debate, JSF fans will get personal first.
It's not about the Brits, at least not entirely, although the "we have a commitment to our main international partner" has always been part of the defense of F-35B.
May I ask what the Marines plan to do with 420 JSFs? This is why the program always officially talks of "680 Department of the Navy" JSFs - there is an implicit and unresolved dispute as to whether F-35Bs replace Marine squadrons in the CVBG air wing. How are mixed STOVL/CATOBAR operations off a CVN a good idea?
Also, the idea of forward-deploying F-35B is rendered dubious by three factors: its F-4-like size and fuel requirement, the unresolved arguments about landing surface requirements and a future combat environment in which FARPs will be targeted by guided rockets and mortars.
The weight and size of the jet limits the numbers that can be carried on an amphib. Even the America-class with no well deck are quoted with a maximum of 22-some jets, but that's with only a couple of rescue helicopters, so it makes no sense: you have a boat full of Marines and equipment and no way to get them ashore.
Now consider those numbers in the only context that is sane: if you need stealth and supersonic speed to deal with the defenses, will the President and Joint Staff ever send in the Marines without a CVN and its Growlers and Hawkeyes?