One of the biggest challenges when creating something new is in not knowing whether or not it’s possible. Once you know, you can just keep pouring resources into it and know with near certainty that you’ll eventually hit your goal. Since the US already has so many other tools for avoiding a nuclear strike, there’s no reason to publicise a new one. Keep it for when the other tools fail, or else everyone else will also have it and you lose your advantage before you could use it.