A claim and "is believed" is not a fact. A fact is that many years prior introduction of that missile (no evidence of being mid-range), the US blocked all discussions about their heavy attack drones which effectively serve the same tasks as mid-range missiles. And the very ridiculous explanation about their mid-range missiles they claimed were built for training purposes, a.k.a "target-missiles". Then it came the question about MK-41 launcher of otherwise air or naval borne Tomahawks, which turned it immediately into a subject of INF (and thus forbidden). The fact that the Russians openly introduced the named missile (9M729), which nobody has seen or have proven has a range more than 500km, AND invited US to a demonstration and inspection of that missile, which US declined, because of course they had other plans ongoing and have already stated they want to leave INF.
More can be added, but please stand the high-ground of a real research on that topic, before repeating the hollow US narrative. A dangerous one as always.
There's more interesting stuff on Wikipedia; this gives the impression that both Russia and USA wanted to exit the treaty because China wasn't bound by it or any similar treaty and thus has been stockpiling exactly these kind of missiles for a long time now, so the treaty puts both Russia and USA at a disadvantage. Then follows some theatrics where Russia and USA point finger at each other while never talking about their true motivation.