Also used to track submerged submarines by detecting ocean surface disturbances caused by the underwater wake of the submarine. Same benefits: works at night and through cloud cover.
When it does, it will be massively destabilizing as it places the "invulnerable" second strike capability that guarantees deterrence against peer states at risk.
It never been such to begin width, at least by the late cold war, some portion of missile subs were reliably tailed by adversaries without any high tech trickery.
North Korea, Russia, and China each already have more submarines than USA, and would have no problem to put 10 subs to tail each Ohio.
It takes a nuclear sub to trail a nuclear sub. NK and China have exclusively, and primarily (respectively) diesel subs. These have to surface and run their engines to charge batteries. They cannot make 20+ knots submerged for long, and they cannot track deeply submerged submarines from the surface. Surfacing and running diesels would make their presence known. They cannot range far from port, and certainly cannot track missile boats under the arctic ice.
Russia has a sufficiently large nuclear fleet, but it is outdated and probably outclassed by US technology. There is probably greater disparity between the powers than existed during the cold war, at which time deterrence was credible.
Even in very well mapped areas, think of the effort in the Indian ocean to find MH370, this would require the assumption that the sub is moving, which is not always the case, e.g. if the sub halts propulsion and drifts with a current.
But there is no need for high resolution and the wake of the sub stands out starkly even with a large field of view. So I'm not sure it can evade detection by halting propulsion and drifting. The point at which it halted would be known and it would be detected as soon as it restarted, unless it was carried by an unknown current far enough to be out of view of the satellite.
Newer ones are directly sensing density, and temperature changes in the seawater by sensing Raman shift, and are supposedly much better. No known data in public of course.