there's a couple of big failures in american defense industry (like shipbuilding) but F35 is not one of them. the alleged killswitch is not likely a thing because first, it could be used by the most probable adversary, and they already shown capability in EW; and second, it's not necessary because it requires constant stream of spare parts and maintenance. as if it's worth it, ask any remaining iranian radar operator for firsthand opinion
some countries switched to euro made jets anyway, but these aren't likely to be doing the job that F35 is cut to do anyway (SEAD)
at minimum brits have source code. couple of eu countries make parts for it as well