In my previous posts about mutually assured destruction I made the point many times over that the US needs to be willing to respond with nuclear force if we're attacked with nuclear weapons. Various people have come up with various retaliation schemes, but the government hasn't made many public statements on the matter.
However, there have been some hints, and they have quite deliberately reinforced MAD -- I'm almost 100% certain that our government has delivered covert threats to many countries reminding them that if we're attacked with a nuclear weapon, they're 15 minutes behind us. For obvious reasons it's to the advantage of all parties concerned that such threats don't leak out.
Anyone who doubts that America has and will follow such a policy doesn't understand how the real world works. The government tries to protect us from a lot of information that would hurt our tender sensibilities, and often does act in our best interests even when we wouldn't recognize them. Good or bad (and many libertarians won't like it), it's the truth.