Comment by dirtyid

>anti-warhead defenses

ABM unreliable, require multiple interceptors per incoming - exchange favors attackers who can always saturate. Also expensive, interceptors usually cost close or more than what they're designed intercept. And currently for anyone not US, just getting US to divert 100s of billions to homeland ABM defense is a win as it will take resources from other priorities. This is also assuming ABM works against hypersonics, including all the recent talk about flak/cloud defense. It's purely speculative.

> blow up one target once

For capital assets that takes billions and years to replace like carriers, subs, supply ships, long range bombers, awacs, critical infra nodes all you need to do is blow it up once. It doesn't take a huge pool of hypersonics to essentially dismantle major US force projection capabilities.

> you just won a nuclear response

Why? Primary motive is deterrence, but with conventional forces. And if it comes down to actually exchanging conventional hits, it will follow escalation ladder, no need to cripple, or cripple to point of existential threat that warrants moving to nuclear.