There is an asymmetry that most people fail to appreciate. If a war were to be fought between U.S. and China, on the Chinese side, you have a continental size country with large number of deployable air, land and naval assets. On the U.S. side, until you get to Australia or Hawaii, we have a handful of airbases and some islands. We also have a surface fleet that is both outnumbered and very vulnerable. Once a war breaks out, all the airports in Japan, South Korea, Philippines and Guam can be taken out. All the surface fleet could be neutralized. This asymmetry can only be altered if there is a generational advantage and very large numerical advantage favoring the U.S.
Going forward, if a war were to be fought, even if aerial refueling made it possible for the B-21 to bomb Chinese assets, in the Western Pacific, the B-21 will have to go without the support of other assets. Our subs could survive in such an environment, but I don't know how our subs can support the B-21.