Well some clean-up is in order here...
Two operational nuclear delivery bombers appear to be missing from this list on the American side of the cold war fence. One is the B-47, the other is the B-36.
Now a lot of people have a tendancy to forget both of these aircraft, as they were intermediate stepping stones for delivery systems of nuclear weapons until the primary system, the B-52, came on line. The B-47 was a very short range aircraft, tis true: it only operated from the forward bases in England, turkey, and the like, but it fulfilled the role quite nicely for about seven crucial years until the big guys came on line. the B-36 Peacemaker was the primary long range nuclear delivery system from about 1947 through the late 50s: it had six turning (six reciprocating engines) and four burning (four turbo jets added later, as an afterthought) to get the job done, but could do theoretically from the US to Russia, with love.
I just have to kiss the person that remembered the B-58 Hustler: It really was a beautiful aircraft to see in flight.
On comment on the XB-70 and the Mig 25 problem: well they made a plane that would be the mach 3 escort for the Valkyrie. They called it a YF-12: this later spun off into the SR-71. I have oftened wondered if the YF-12 would have actually outrun the bullets fired from its internal gatling gun, but....
I do believe the Mig 25 would have had a bad time dealing with this SR-71 variant.
The russians had many good cold war bombers: we need someone to speak up for them.