Russia's nuclear arsenal is not as credible as the US's nuclear arsenal. They have a lot of warheads but have limited ways of delivering them to their targets. China has the same issue, which is why the US establishment does not fear nuclear war with either country. They know that in the end, they will win.
As of mid-2021, the Russians have 339 operational nuclear-armed ICBMs and the US has 400 operational nuclear-armed ICBMs. None of the US ICBMs are MIRVed (and therefore contain only 1 warhead), while hundreds of Russian ICBMs are MIRVed, all with warheads (~20x RS-18 with 6 MIRV warheads, 46x RS-20 with 10 MIRV warheads, ~99x RS-24 Yars with ~3 MIRV warheads, ~18x RS-24 Yars with ~3 MIRV warheads, and ~54x Yars-S with ~3 MIRV warheads).
That's 1,195 nuclear warheads on its ICBMs for Russia (1093 MIRVed and 102 unitary) while the US has only 400 unitary warheads on each ICBM.
Clear numerical superiority. All of those ICBMs have the ability to hit anywhere within the US (same with the US against Russia) so there's nothing inferior there either. They also average noticeably higher nuclear yields than the US. Note I only included operational warheads, not any experimental stuff the Russians are producing.
In terms of nuclear-armed strategic aircraft, the Russians have 76 nuclear-armed strategic aircraft (9 Tu-160; 7 Tu-160 mod; 42 Tu-95MS; 18 Tu-95MS mod) and the US has 66 (20 B-2A; 46 B-52H). The US has ~528 AGM-86B ALCMs with a range of 1500+ miles to arm their 66 bombers, the Russians have ~600 nuclear-armed KH-55SM and KH-102 ALCMs, with published ranges of ~1800 miles and ~2,800 miles, respectively.
Once again, no clear inferiority, in either numbers, range or magnitude. You can take as many grains of salt as you like, in regards to the published ranges being fake, or the inventory being pumped, or even frauding the warhead yield. You can assume their maintenance is so garbage that many of the warheads will fail to work or the missiles will implode before they even leave Russia. All this still would leave Russia in the ballpark of total US nuclear strategic capability.
The last area, SLBMs on SSBNs, is the place where the US has superiority. 14 Ohio with up to 20 UGM-133A Trident D-5/D-5LE nuclear SLBMs each (280 SLBMs max) all with MIRV capability of up to 14 warheads. On average though, each missile only carries ~4 warheads (due to treaty limitations). That is ~1,120 warheads. The Russians have 11 SSBNs (1 Kalmar; 6 Delfin; 3 Borey; 1 Borey-A) with 16 SLBMs each (of varying types) for a total of 176 SLBMs and a total average warhead count of ~816 warheads (slightly higher MIRV warhead count than the US). Range for the US and Russia is not very relevant, the worst SLBM (with Russia) can hit Florida just 500 miles north of central Siberia.
As you can see, nuclear war is one area the US can't win. US population density is also vastly higher, land area in overall size is much more limited, and urbanization is higher as well. A nuclear war with Russia would end for all time the US, but would not end Russia despite crippling it for many decades (assuming climate catastrophe from a nuclear winter is overhyped, which it certainly is).
