The way I look at it is if we can drive around and fly helicopters on Mars, deploy advanced folding space telescopes for optional science, what we do for necessary defense of 340M people (and our allies) will far eclipse that in both technology and expenditures over many decades. Hypersonic missiles aren't exactly slow since they are traveling 3 to 5 times faster than an AR15 bullet. Try intercepting a bullet some time (not with your body), let alone one traveling 4x speed!

We stopped reporting on "Star Wars" back in the 80's but research is unrelenting. There are many ways to destroy missiles now—kinetic, beams, EMP, particles, flack. swarms, you name it. I suspect much more has gone into defense than offense because of rogue weirdos like Kim and others. Also intelligence is our greatest asset, tracking every known location of missiles, warheads, supply, reactors, submarines, etc.