All these stories admit these were the people that fought with Al Qaeda's Iraqi branch (supported by Assad etc.), were imprisoned by the US, and decided to keep fighting after being released. 'Conclusion': US created ISIS. Right. Maybe Iran and co. should have been more careful with their choice of proxies.

No, the articles say that ISIS has been created in Bucca. From the Guardian article:

“[al-Baghdadi] was respected very much by the US army,” Abu Ahmed said. “If he wanted to visit people in another camp he could, but we couldn’t. And all the while, a new strategy, which he was leading, was rising under their noses, and that was to build the Islamic State. If there was no American prison in Iraq, there would be no IS now. Bucca was a factory. It made us all. It built our ideology.”

Yep, it's an evolution of Al-Qaeda in Iraq (that's why all these people were in jail in first place), built under their noses [their = the US]. In English, that means it was hidden from the US, not complicity.

Now, if Assad and the Mullahs didn't support Al-Qaeda in Iraq in the first place, or if they got their Iraqi pawns to keep the lid after the US left, maybe the jihadists wouldn't have been strong enough to create ISIS later on.