Nuking Megaton and the Citadel worked wonders. Bombing any other town would work the same way. In today's world, if a a place got bombed, you'd have white knights galloping to the rescue, but not in Fallout. If, say for example, Camp McCarran got bombed, that place would be done. Some troops would survive, yes, but McCarran would be useless.
Think size. Megaton was miniscule, not a town, more a hamlet, the Citadel was absolutely tiny as well.
A city? An actual city? Using a single bomber on a city is about as effective as throwing mud at a wild bear. Fun and it makes cool noises but in the end you're just gonna piss it off. Of course in Fallout many areas are destroyed, smaller places could be successfully bombed but actual to scale cities would laugh off the attack of a bomber (ok, it would hurt and it wouldn't be funny, but it wouldn't devastate anything).
Assuming, of course, it isn't shot down. House has the tech, the BoS likely do and I'd be surprised if the NCR didn't have a few weapons kicking around that could shoot down a rusty old bird.