In the US, there is a legal distinction between child pornography and child obscenity. Both are criminal, and exceptions to the 1st Amendment – but, the first is much easier to prove in court. In the 2002 case of Ashcroft v Free Speech Coalition [0] SCOTUS ruled that (under the 1st Amendment), child pornography only included material made with real children – so written text, drawings, or CGI/AI-generated children are not legally child pornography in the US. In the US, child pornography is only images/video [1] of real children. If someone uses editing software or AI to transform an innocent image/video of a real child into a pornographic one, that is also child pornography. But an image/video of a completely virtual child, that doesn't (non-coincidentally) look like any identifiable real child, is not child pornography in the US.
What most people don't seem to know, is that while a virtual child can't be criminal child pornography in the US, it still can be criminal child obscenity – which is rarely prosecuted, and much harder to prove in court, but if they succeed, can still result in a lengthy prison term. In 2021, a Texas man was sentenced to 40 years in prison over a bunch of stories and drawings of child sexual abuse. [2] (Given the man is in his 60s, that's effectively a life sentence, he's probably going to die in prison.) If someone can get 40 years in prison for stories and drawings, there is no reason in principle why someone could not end up in federal prison for AI-generated images too, under 18 USC 1466A. [3]
[0] https://en.wikipedia.org/wiki/Ashcroft_v._Free_Speech_Coalit...
[1] maybe audio too? I'm not sure about that
[2] https://www.justice.gov/opa/pr/texas-man-sentenced-40-years-...