Only 400? That's still quite a few...
Not in comparison when the US had 1054 land-based ICBMs.
We should have at least 4 Trident sub boomers SSBMs out on station at all times and they better be undetected.
If the Russians or the Chinese in cahoots with Russia ever figure out a way to track and tag those boats, you can bet your bippy that Putin would contemplate a first strike on the US, and those 400 land-based ICBMs and bomber bases would be vulnerable to nuclear destruction. It’s a short hop skip and a jump and say good bye to the United States. Putin could and would envision an old Soviet dream dreaming the total destruction of the United States.