"Most of Russian nukes are there in silos, on the ground in more or less pre-determined areas"
"RPKSNs parked in Barentz sea bases (it's too expensive and dangerous to keep them at sea and they can't get anywhere close to US coast anyway)"
"Bases of strategic bombers are also known"
these are all baseless assumptions. nobody can assert with confidence that all russian nuke silo locations, nuke sub routes and strat bomber air bases are known and accounted for.
claiming that america could first strike russia so effectively that retaliation would be impossible is insane, and claiming that american countermeasures will reliably protect against retaliation is just wishful thinking.