Russia can only send several hypersonic missiles before European and U.S. subsonic missiles are fired back at Russia. Western military has far more missiles than Russia will have hypersonic missiles so then it becomes a conflagration of “conventional” weapons. That’s the great part of the threat of mutual destruction—no one wins, everybody loses. It’s also the reason why the U.S. should avoid nuclear missile treaties with countries like Russia and China. They will cheat just like Iran cheats, and by the way, they all get away with cheating.