If you use any copyrighted source material without appropriate licensing (note: Fair Use is a form of licensing) in any way, that's copyright infringement. This is very simple and the legal world has demonstrated that fact time and time again long before computers ever came onto the scene.

Some "AI" drawing a picture derived from copyrighted materials is no different from a game using copyrighted assets from another game. If there is no appropriate licensing, it's copyright infringement.