Cerny worked even in Sonic 2 as programmer, like in Jak. In Ratchet he was designer. In Spyro or Crash he vas executive producer, the main role he had in most games, specially most recent ones (stuff like Spider-Man, The Last Guardian, Rift Apart). He also worked as design consultant in games as Uncharted, Resistance, Gow 3 or Killzone 3.
Knack and Knack 2 are the only games where he was the director, meaning he had more freedom to do whatever he wanted. I assume Knack 1 started as a PS4 tech demo to test stuff they were building for it, and someone owed him a favor so allowed him to direct a game. For some reason (massive bundles) it sold many copies even outselling the Mario of that time Super Mario 3D World so allowed him to make Knack 2, maybe hoping it was going to be much better. And well, watching the results maybe someone forbid him to go back to Japan xD
After Knack 2 he worked on Spider-Man (executive producer), Death Stranding (tech producer), Morales and Rift Apart (Executive Producer), plus appears in the Special Thanks of Ragnarok and HFW. Now he's working with Haven because apparently their gamedev tech apparently is amazing and heavily boosts productivity, so he may be helping them while also preparing it to give it to the other Sony teams.
And well, since he designed the hardware architecture of PS4, Vita and PS5 I assume he's designing now PS6 too. This guy is a genious.