1. Total counter-strike--against Russia and any and all of its allies. The nuclear deterrent will only work when the otherside realizes that any strike will spell out its own doom. The fact that the US population will be already dead, and the deterrence has failed in one instance changes nothing. Nuclear technology will still exist, and the deterrence model must be upheld for the sake of the remaining world.

2. Why would the response be different? The deterrence model needs to be reinforced.