Awww, c'mon man I know it's boring down here in my land of Newtonian mechanics? But at least the math isn't controversial.

800 warheads in Russia, 600 on subs, 200 in bombers. I think we can agree that a coordinated first-strike by Russia is not going to go off smoothly. I think we can also agree that the most likely successful launches are going to be from subs. An R29, launched from the geographic center of the Gulf of Mexico, will hit San Antonio in 2 minutes. And, by the numbers above, will have around 1400 friends.

What does a practical deterrent against that look like?

Fuckin' Darth Vader couldn't pull that shit off with the Death Star. An Iridium constellation made of Death Stars is going to have a tough time killing 1400 penetrators. Let's assume whatever we have is as good as Iron Dome (85%) because improvised Hamas ballistic weapons, Russian ICBMs, same same. I'm gonna need about 1700 somethings, I'm going to need them with close-kill capability against stuff coming up 20 miles offshore at 15,000 mph, and they're all going to weigh as much as a Miata.

There's a reason we abandoned missile defense. Wanna see it?

Russian/Soviet/Russian doctrine has always been "stack bodies." At the time we were seriously contemplating deploying Sprint missiles? The USSR had 47,000 warheads. Because we're American, we decided that since we couldn't defend everyone there was no fucking point. Because they were Soviet, they decided they only needed to defend Moscow. Doctrinally? They have an advantage. "Defend the Kremlin" is a much easier task than "defend the fourth largest country by land mass in the world."

You wanna know what a secret defense system looks like? It looks like first-strike. If we had anything up there - and we don't - it would have one job: Kill Moscow. You can talk about error bars/uncertainty but this was an entire industry for 50 years, it's not like this shit hasn't been wargamed a dozen different ways.

And you're not going to spend any money without wargaming it a dozen different ways.

There's no magic bullet, man. The minute either side decides to launch a first strike, the other side will launch a last strike and the future is up to the cockroaches.