Given the type of both recent and predicted conflicts that the US has been involved with, it's not 100% clear to me that the US needs yet another aircraft. That is, fighting in proxy wars or fighting in countries like Iraq, Afghanistan, or Syria don't need anything new. And fighting a sophisticated enemy would probably ramp up to nuclear deterrents and diplomacy anyway...fighters wouldn't make a notable difference in that kind of war.

Won't happen, but it seems like they should just buy fighters from allies where the F-35 isn't a good fit.