As it was said earlier - "To be effective deterrence must be credible, and to be credible - it should not be suicidal". It is not the question - "Can the USA destroy Moscow in unprovoked out-of-blue attack?" Yes, they can. The real questions are:
1) Can the USA attack Russia in the way, after which Russia won't be able to cause unacceptable damage to the USA? (And what level of damage is acceptable to USA in the current situation?) Answer is "no" for first question, especially if "acceptable damage" in the current situation is pretty low (and it is very low, when we are talking about Crimea and Novorussia and not about Alaska and California).
2) Can Russia attack USA in the way, after which the USA won't be able to cause unacceptable damage to Russia? (And what level of damage is acceptable to Russia in this situation?). And answer is "yes", Russia can decrease possible losses after retaliation strike of survived US nuclear forces to the level much lesser than 20 mln killed (even in pessimistic scenario) and this level is pretty acceptable, if we are speaking about Crimea and Novorussia (or even the very existence of Russian Federation) and not about Alaska and California.
So, if we are talking about details of the video....
1) Moscow, however valuable, is expendable. Napoleon burnt Moscow back in 1812, but lost the war. Biden still can burn Moscow, but, highly likely, it will mean defeat of the USA in the war and, may be, even extinction or American people.
2) 8 warheads per missile means pretty short firing distance and at this distance US SSBN are more vulnerable. Highly likely, that in the Pearl Harbour scenario (US retaliation strike) SSBNs in foward patroling areas were killed before launch.
3) Moscow's ABD can intercept at least 100 incoming warheads. Which means that typical salvo 20 missles x 3 = 60 100 kt warheads of one SSBN will be definitely intercepted.
4) If we are not talking about American out-of-blue attack against sleeping Russian cities (and this scenario is not possible because of many reasons) it means that state-essencial personal (and not city-essencial) personel will be evacuated before US retaliation strike. And city-essencial personel will be sheltered.
So, more likely, that those few survived warheads won't kill more than 100k (mostly state non-essencial) unlucky civilians in Moscow. And Russia already proved that 100k is the pretty acceptable level of losses.