We know about them now.None of what you listed has to do with our ability to stop nukes. Note also that we know we have those things, so using them as an argument that the US is sandbagging doesn't work.
We're working on one, but still, it's woefully inadequate from what I can tell. Which, fair enough, some of this is new tech, and there's a ton of political problems that need to go through.
Don't get me wrong, the GMD program is absolutely great at what it's designed to do: stop a country from getting a few ICBMs then holding the US at gunpoint forever. What it isn't, that people keep pretending that it and other anti missile programs are, is a Russia/China nope button.
But at that time, who would have thought we were able to do such things until it happend?
The military is ready for things.
A whole hell of a lot.
We have the largest military budget in the world for a reason.
There is shit we have that is probably more advanced then what we know about.
We just keep it secret because we don't like to brag