More recently, the Office reviewed a registration for a work containing human-authored elements combined with AI-generated images. In February 2023, the Office concluded that a graphic novel 9 comprised of human-authored text combined with images generated by the AI service Midjourney constituted a copyrightable work, but that the individual images themselves could not be protected by copyright.

--- from Copyright Registration Guidance: Works Containing Material Generated by Artificial Intelligence

https://copyright.gov/ai/ai_policy_guidance.pdf