First, agreed we don't want to go there. I'm just responding to the concept that "Russians are preparing for a nuclear war" - suggesting that if they prepared enough, that would allow them to ultimately "prevail."
Even if we assume away the environmental impact, the only way to prevail is to destroy your opponent's nuclear force before they can launch. Today, that boils down to destroying the US submarine force that is deployed at sea. If you can find and destroy all those missile boats before they launch, you can prevail. If you can't, then your nation will be destroyed. Its a very simple story.
Attacks on US soil, while very disagreeable for us, won't enable an opponent to "win". The Topol-M does not target the sub force, so as a "first strike weapon", its more or less useless. As you point out, it is great for targeting cities, but that won't allow anyone to "prevail" since it leaves the US sub force intact.
Topol-M is probably more survivable than the SS-18 (or the follow-on Sarmat) since it is mobile, while the heavy SS-18/Sarmat missiles sit in a fixed position in a silo, and would easy to target.
I'm sure Dogs knows vastly more than me, but I also suspect he's unable to comment.
So to summarize:
Will civil defense allow Russia to prevail? No.
Will targeting US cities (with Topol-M, or SS-18, or Sarmat) allow Russia to prevail? No.
Will striking first by surprise using submarines at the US continent allow Russia to prevail? No.
If it doesn't target the sub fleet, it more or less doesn't matter - at least when it comes to a first strike anyway. So "preparing to fight a nuclear war" = won't change the outcome in the slightest. Both sides would be finished as civilizations, period. All these "preparations" are thus meaningless.
A widespread deployment of a viable ABM system for ICBMs - and that means hundreds of launchers, that are proven in testing to have a high success rate at interception - that might change the math. But no such system exists, on either side - at least no system that we know about anyway - and certainly not the S-500, which remains vaporware.
Here's an article that describes the progress of the US ABM program:
http://nationalinterest.org/feature/the-limits-us-missile-defense-12503
Israel has several anti-missile defense systems - Iron Dome for the little stuff, and the Arrow series for long range missiles. Arrow 3 is an exo-atmospheric interceptor for ICBMs - a recent test had it successfully intercept an incoming warhead, picking the actual warhead out from a group of decoys, which is a hard task. But even that system has yet to be deployed.