If you have updated satellite imagery and can hit the SAM with a cruise missile you don't need the B2.
Do we have this class of anti-radiation weapon?
If the radar is mobile, that means that you need a true anti-radiation missile, but SAM radars aren't mobile, are they?
Also only the radar really transmits, so even if you hit it the, separate launchers might still be intact & guided by another radar if you don't destroy them.
This is why modern remotely guided middle strike drones are so dangerous for SAMs - they can basically search an area for all the SAM system components and destroy them all or most of them. Potentially much more effective than a homing missile hitting just the radar at maximum.