The US hypersonic missile programs seem to be like the SLS (Space Launch System). The US hypersonic missile program and the SLS are not delivering consistently successful tests or deploying successful systems. China and Russia have deployed basic hypersonic missiles. The US is spending $15 billion between 2015-2024 and more money was spent before 2015. Prior to 2005, the argument was that hypersonic missiles were to hard and complicated. The US kept pursuing complex triple engine solutions. China and Russia chose to not have two other engines in the mach 0-3 stage and another for the mach 4-5 stage. China and Russia went for a rocket to get the hypersonic stage to mach 5+.

I think the US hypersonic program not succeeding because it is like Boeing failing to deliver the super heavy SLS rocket (space launch system) after 11+ years. The SLS rocket should have been straightforward by reconfiguring a Space Shuttle into an Apollo rocket stack. Boeing and other old school space and military companies have had major problems delivering new military planes and have not made new rockets for 20 years.