Valkyrie was a different class of bombers, one that never came to be. Rather than the Blackjack, the Russian answer to Valkyrie was actually the T-4. The SR-71 was a spyplane, but there was also to be an SR-71-class interceptor meant to shoot down incoming Valkyrie/T4-class bombers. That entire field of mach-3 bombers and fighters was stopped by advanced in missile tech.

https://en.wikipedia.org/wiki/Sukhoi_T-4