Realistically, I think what would have to happen is that Congress would have to pass the measure as an official government policy. More as a deterrent than anything else. But if Congress were to come out and pass a measure that stated that the President was authorized to use all the weapons at his disposal- including nukes- against all targets, including symbolic ones, it would have a dramatic effect. I believe it would anyway. You might have to pick a target in the middle of the Sahara, far away from anything and let off a tactical nuke, just to demonstrate that you are capable of doing it but I believe it would definitely have an impact.
Actually, there are safeties in place to prevent unauthorized launches. However, the political leadership has final call on a launch provided that the President is in possession of his faculties and the provocation is clear.
The 509th Bomb Wing has 20 B-2 Spirit bombers, some of which are on strip alert at all times, provides the President with his greatest menu of choices. That's the unit to watch.
When you see those bombers being dispersed to bases around the country from their home field at Wightman AFB, that's the time to realize that the SHHTF (sh#t has hit the fan-past conditional tense, I believe).
The role of the bomber gives any President, especially this one, a range of choices and targets. Each B-2 carries a carousel of ALCM's that are armed with warheads in the 50 to 300 kiloton range. The day of the bomber flying over the target, opening the bomb bay doors, and dropping Major Kong and the "Dear John" on the missile silos at Laputa are long gone. Even the BUFF uses the carousel launched stand-off missile.
The idea of responding by a staggered barrage of ICBM's based at silos in the Dakotas and in Montana is a non-starter. Their flight paths are polar and would take them over Russian airspace. We wouldn't want to get STAVKA all alarmed. Bad political mojo, that, especially since the Ivans would be "silent partners" in any American retaliation. Any Russian government would know that Russia would be "next" on the Islamic hit list, so they would understand. But ICBM's over Russia would get the Russian political class nervous, not to mention the General Staff.
SLBM's based in the Indian Ocean are an attractive option. MIRV'ed missiles, such as Trident D-5, have ten warheads a pop and have an extreme range. Targeting is merely a question of downloading the proper coordinates.
Part of the problem here is that the Rags have no earthly idea of the forces they toy with. That has always been the main issue; it's such a neat idea to destroy Christianity and replace it with a militant, fascist Islam that the advocates of such a course never thought of the consequences of the attempt. The Muslims are so caught up in their dream fantasy that no one appears to be able to tell them how this conflict will conclude. See, the Islamists actually believe that they can force us to choose between our survival, and theirs, and walk away unscathed.
This war will end in one of two ways: with America triumphant and the Islamic world on its way to an Islamic/Arab form of representative government, or with America triumphant and the Islamic world reduced to a marginal, radioactive existence in which the living envy the dead.
There literally is no other way.
Be Seeing You,