The B-52 would have a problem with modern air defenses. It would be best as a missile platform, bringing large loads of cruise missiles near the target while staying out of range of enemy AAM. It would also be good for leveling places without modern air defenses.
Excellent Point. By the time B-52s reach their targets nothing would be left of Russia and there would be not too many operational air bases funtioning in the United States.
Some Russian SLBMs would strike civilian airport runways that are at least 7000 Ft long. This is the minimum length required by B-52s; there were 210 such runways in the U.S. in 1977. During a crisis, big bombers would be dispersed to many of these long runways, and enemy SLBMs would be likely to target and hit these runways in an effort to destroy the maximum number of bombers. I have a plan to bring back any surviving bombers who managed to complete their objectives home but its only a plan.