The last truly successful US bomber program was the B-52.
That should be telling enough. Try to look at how many bomber programs the US had which failed like the B-58 Hustler.
I am fairly certain the MIC will find some way to make the B-21 so expensive to maintain and produce it will become another niche program.
Of course by that measure the last successful Russian Bomber was the Bear.
Hustler failed as it failed to consider the advent of the SAM site. The B52 proved able to be modified for extremely low level. XB70 failed as again air defenses changed. B1 was Lazarus by comparison it rose from the dead. It’s only real failure was that by the time it emerged Stealth was coming and the ICBM was in full swing. The B66 and the others were products of the time when technology of jet and supersonic aviation changed as fast as computer technology of the last 30 years.
Oh yes the failure of B2? The end of the Soviet threat and economy meant that the B2 was no longer needed. The main mission threat that once justified a huge fleet of B2 fell so hard into decline they had to pay their debts to Pepsi co. in super tankers. Slashing orders increased cost for tooling and production driving costs up on B2. 21 B2 were built, like the F22, Zumwalt or Seawolf that drove the costs mind bogglingly high.