The USMC has a long corporate memory of the "big navy" air cover leaving them unprotected at Guadalcanal apart from the Cactus Air Force. Plus, for a small scale bespoke intervention, a MAU is a lot cheaper to deploy than a CBG - even if one were available.
As for the USAF; well, they've been trying to actively kill the A10 since birth (because it isn't an F16...) so there's no little irony in them now templating its role and capabilities against F35B. I do think the USAF should be looking at a genuine A10 replacement - one that doesn't need first day LO, can carry a decent weaponload, good endurance and is affordable to both buy and operate. Surely there's a place for something between AT6 and F35A?
FWIW, I can forsee a future where the RAF buys F35A as the Typhoon replacement so we have a one-type FJ fleet circa 2030.