That's the thing. They don't care...in fact our enemies would love to use that as an excuse to attack us. I am all for protecting our troops from attack but a nuclear response could escalate this into a world wide conflict....a world wide nuclear conflict. These are hypothetical roads I would rather the US not travel.
The people in the field who would have to "push the button" to carry out such an order are not in that position -- they're ordinary officers who have a reasonable hope of mercy if captured... unless they commit this war crime.