The problem is who is sufficiently stupid to actually attack USSR? (and what date are we talking about 45-80 is huge with big changes in the balance of power?)
NATO is only a defensive alliance the real risk of it not wanting to fight WWIII to protect somebody who openly attacked the Soviets would be very high, US might support them but once we get to late CW MAD they need to decide if New York is worth losing to avenge Iran or Pakistan.....