Russia claims to have fired hypersonic missiles in Ukraine

The USA currently does not have hypersonic missiles in its inventory although they are in development. How is this possible that the US does not possess them and Russia does??? “Russia's Kinzhal is allegedly designed to overcome any known or planned US air or missile defense systems including MIM-104 Patriot, Terminal High Altitude Area Defense and Aegis Combat System. The US's multi-purpose SM-6 missile is the onlyweapon in the country's arsenal at present that offers any ability to
knock down highly-maneuverable hypersonic threats."