Ok - let's say that the retaliation is purely aimed at military installations and comes after a completely successful US first strike. God help us all, but let's think this through.
Only one of the Borei submarines would be on patrol, it's reasonable for there to be some failures, but even with a 50% fail of missiles and warheads 30+ nukes would be hitting the USA.
I imagine that the targeting for Russian SLBM's is calculated to cause maximum loss to the USA - maximum loss of life and economic damage. I imagine this because if I were Russian that would be the message I would want a US president to have when calculating this, but it is just possible that there is a military targets only war plan, and this is the scenario you are exploring here.
In this scenario the minimal retaliation would be 30 ~200 kt warheads striking military bases - like San Deigo, Puget Sound and so on. Each strike would probably result in ~5k dead and 100k other casualties. So, minimum, 30 craters, 3 million casualties and 150k dead.
That's three Vietnams in an afternoon. Now, discount the stain of murdering many more Russians (because the successful first strike would involve many strikes that would result in large scale civilian deaths), I find it really hard to think that any rational human could contemplate causing the death of ~150k fellow citizens for "the greater good".