I believe the hypersonic missile launched in Ukraine was a standard ballistic missile launched from an airplane and is really nothing that advanced (the article mentions this technology was invented in the 80s). Hypersonic glide vehicles are more of a question mark. Russia claims to have them, but their ability to reliably deploy them is unknown as they’ve never been used outside of tests. The U.S. is working on its own HGV, which should be superior in many ways. This attempt at achieving superiority is also what’s leading to the lag as more technical problems need to be worked through.
What you see here is a difference in doctrine, not better or worse systems.
US has heavily invested in their second strike capabilities, and is far ahead of Russia on that.
US has largely viewed investment in first strike capabilities as a waste, the DPRK is their only adversary that could possibly be decapitated with such weapons.
A first strike against Russia would result in an unstoppable second strike, what good are first strike weapons in this scenario?
The Mattis quote in your article provides a good tl;dr
>U.S. Defense Secretary James Mattis stated Russia already has the capability to hit U.S. port cities with missiles, and said that Poseidon "does not change at all the strategic balance".
US is already incapable of stopping “regular” ICBMs, poseidon does not change the calculus at all.
https://en.wikipedia.org/wiki/Status-6_Oceanic_Multipurpose_...
https://www.axios.com/kinzhal-hypersonic-missiles-russia-ukr...