Sonar networks track Poseidons plus submarine superiority and nope SB-AMTI is targeting too. One a cruise missile is tracked, any fighter can shoot it down.
What fighter? There won't be any organized interception effort in place for the envisioned use case. Search and track are entirely meaningless without kinetic interceptors. And while you seemingly try to ignore that for like 3 pages straight, the assumption that after the first and second wave of a strategic exchange there would be much left of the USAF, USSF, strategic command is approaching the realm of willful fiction. The only thing left would be USN submarines, simply because they're too numerous and too survivable to be destroyed wholesale (although any unfortunate submarine in port would most likely be destroyed).
Assuming SB-AMTI survives every orbital platform being targeted and remains operational for long enough (despite nuclear warheads going off in space, direct ascend Anti-Satellite weaponry being used and vast debris clouds sweeping through every level of earths orbit) to track and designate an entire wave of Burevestnik being launched (presumably as part of/a system similar to Perimeter), then what? US command structures were targeted, overwhelmed and wiped out in the first wave of the exchange. CONUS based assets of the US armed forces like the major airbases housing tactical and strategic aviation are among the targets as well. Assuming that SBI would've become a reality and some what operational, the interceptors would've been depleted and the satellites for the most part would've gone out of operation.
Are you suggesting that a man in rural Texas will shoot down a nuclear powered cruise missile with his shotgun when it approaches over the southern border several days up to weeks after a full scale strategic exchange which killed millions initially and millions more after food, water, medical and sanitary supply chains collapse, that would have destroyed the majority of US based force structures and military assets? Who would SB-AMTI track for,
assuming it's still there. Who would take over the kinetic intercept when there would be few surviving military installations and it's more than doubtful these installations would remain manned after a nuclear war. No satellites, no jets, no SAM sites.
The only plausible way to counteract this would be to have dispersed and hardened start ramps for something like X-Bat, which could be controlled by a dead hand system as well. But then you have Burevestnik which can simply out-loiter such drones due to it's propulsion. Realistically there is no plausible counter to this kind of weapon the US has or could deploy now or in the foreseeable future (submarine SAM anyone?)
And this is the whole point of it, it's meant to greatly complicate strategic defense efforts and introduce a flood of variables an adversary has to account and budget for, which is impossible and especially impossible for the US which has to fund all sorts of wonder weapons across all it's branches at exorbitant costs with increasingly dragged out timelines and near decade long delays. And compared to all of that, Burevestnik is a simple and low cost investment that ensures that imaginary multibillion Star Wars systems would only counter a fraction of one aspect of the entire strategic portfolio (a limited amount of ICBMs in that context). The US has put itself into the role of the defender, as it's strategic offensive capabilities have been outpaced greatly by it's main adversaries decades ago. Unfortunately, by it's very nature, the defender is at a huge disadvantage when it comes to investing resources and funds. Meanwhile the Russians concluded that overwhelming and unorthodox offensive capabilities in the realm of strategic warfare substitute any defensive posture for significantly less cost. That's what a strategic deterrent is all about, this is text book Cold War stuff. Hoping, praying and sinking several billions of dollars into Wunderwaffen and conceptual silver bullets is the opposite of that, and the US attempted that already once and concluded that SDI was a waste of time, money and resource. Obviously and evidently in this forum in threads adjacent to the topic, the matter still captures the imagination and dreams of the generation old enough to have been a child back then. Anyone born after that has little nostalgia for it, as do the people that ended that fever dream back then.