There is nothing that makes hypersonic reentry vehicles uniquely difficult to intercept, I'm not sure why anyone would assume that. The US considered this a sol

There is nothing that makes hypersonic reentry vehicles uniquely difficult to intercept, I'm not sure why anyone would assume that. The US considered this a solved problem in the 1980s. As for the US being "behind", the US was developing and testing endo-atmospheric hypersonic missile platforms as far back as the 1980s. Russia et al designed hypersonic weapons with significantly compromised terminal guidance performance, a compromise the US will not accept in operational systems. Terminal guidance is the hardest technical problem when designing long-range endo-atmospheric hypersonic weapons. That the US is starting to move these systems toward production after 30-40 years of research suggests that they've solved the problem of terminal guidance to their satisfaction.