[Targan]

Perhaps the greatly superior accuracy of NATO's nuclear weapons resulted in a higher proportion of Soviet missiles being destroyed in their silos? Then again, you'd think that widespread NATO strikes on Soviet launch sites would escalate the exchange to a much greater level than described in canon.

There is a lot more specific canon info available about post-exchange USA than the USSR. Perhaps there are still many warheads intact in the remnants of the Soviet Union but their delivery systems are no longer functional? Also, the USSR covers a vast geographic area and we know that vast tracts of Soviet territory were no longer under central government control by 2000. Hundreds of Soviet nuclear warheads might be in the possession of dozens of factions of various legitimacy.

I don't know much about the durability of ICBMs or what sort of ongoing maintenance they require. How long after standard command and control and supply lines collapse before ICBMs become too dangerous to attempt to launch? Can they sit in their silos for a decade with little to no maintenance and still be safely launched? Obviously warheads designed for more conventional delivery systems would probably be more useful by 2000 (it's probably easier to verify the launch-worthiness of a cruise missile or a strike bomber than it is with an ICBM).

There are definitely canon descriptions of successful ASAT attacks, but not much to suggest that there were comprehensive space-based ASAT systems in place. I wouldn't consider it to be canon-breaking to suggest that limited, experimental space-based ASAT systems were in place at the start of the war. I had an NPC in my last campaign who was proud of the fact that he'd 'killed' a Soviet satellite with an aircraft-launched ASAT missile earlier in the war. Later when those kinds of systems had been expended/destroyed he'd been transferred to Europe as a USAF fighter pilot reinforcement before his F-15 had suffered a critical mechanical failure over Poland.