Only Congress and the courts do. Copyright exists from the moment a work is created, and does not need to be registered with the copyright office.
The law isn't that complicated; if a work was created with a human being with intent, it's probably eligible for copyright protections.
As long as you can convince a court that you did this, the tools you used are not relevant. The vast majority of LLM art falls in this bucket.
> Whether human contributions to AI-generated outputs are sufficient to constitute authorship must be analyzed on a case-by-case basis
It says a plain prompt is not enough but that is not the reality of real software development. People aren't one-shotting complex business apps. The vast majority of software development will trivially pass that bar and end up in the "requires case by case analysis".