It looks imaginary. Or, if you prefer, it looks hypothetical.
The point isn't how we would respond if this were real. The point is, it isn't real - at least not at this point in time, and it's not looking like it's going to be real tomorrow, either.
I'm not sure what purpose is served by "imagine that I'm right and you're wrong; how do you respond"?
On some things that is not a bad position: The old SDI had a lot of spending but really not much to show for it while at the same time forcing the USSR into a reaction based on what today might be called "hype".
The particular problem arises when both actors in the game have good economies and build the superweapons. We happened to somewhat luck out that the USSR was an authoritarian shithole that couldn't keep up, yet we still have thousands of nukes laying about because of this.
I'd rather not get in an AI battle with China and have us build the world eating machine.
It looks imaginary. Or, if you prefer, it looks hypothetical.
The point isn't how we would respond if this were real. The point is, it isn't real - at least not at this point in time, and it's not looking like it's going to be real tomorrow, either.
I'm not sure what purpose is served by "imagine that I'm right and you're wrong; how do you respond"?