I’ve used them a few times to bomb Germany into the stone age. Especially on a KJF strategy.
England pumping out 1 or 2 bombers a round up to 3, America keeping 2 or 3 bombers in England and then blowing the heck outta both Germany facilities will severely limit his production. Heck, 6 bombers vs Germany herself is still 20 damage, that’s 6.66 infantry they are not buying to prosecute the war. And remember, those rounds you don’t loose a bomber, you don’t build one, you build fighters or transports or land units instead.
Meanwhile, America is more then capable of taking out Japan. If Japan switches to building navy they do not have the man power to make significant gains against Russia/America/British stonewalling and thus America can easily out produce them, especially when America starts grabbing islands.