Or maybe there is a real threat that unbiased experts now recognize as a threat, after all it is very arrogant to doubt the advanced engineering and determination of both Russia and China to develop hypersonic weapons.
Historically the US has flown ramjet missiles to M5. It just took a stuck fuel valve and IIRC worked quite well (till it ran out of fuel)
The problem with hypersonic flight is not that it can't be done, it's when people insist on doing it in the atmosphere and using a SCramjet to do it. If you're OK with using a rocket it's (relatively speaking) not that difficult. If you want longer range in the same package then ramjets can already do that with reasonable T/W.
Engineering a long range hypersonic missile using a conventional ramjet is within the current SoA. The toughest part is likely to be the structure and the TPS.