I suspect with a creative enough prompt you will likely be able to claim copyright and author ship over the works.

It seems that's not the case, no matter how much effort or time you expend on the prompts. This is from the Copyright Office:

The Office does not question Ms. Kashtanova’s contention that she expended significant time and effort working with Midjourney. But that effort does not make her the “author” of Midjourney images under copyright law. Courts have rejected the argument that “sweat of the brow” can be a basis for copyright protection in otherwise unprotectable material.18 The Office “will not consider the amount of time, effort, or expense required to create the work” because they “have no bearing on whether a work possesses the minimum creative spark required by the Copyright Act and the Constitution.”

Here's another key factor:

Because of the significant distance between what a user may direct Midjourney to create and the visual material Midjourney actually produces, Midjourney users lack sufficient control over generated images to be treated as the “master mind” behind them. The fact that Midjourney’s specific output cannot be predicted by users makes Midjourney different for copyright purposes than other tools used by artists.

This only applies to an image generated with AI prompts that isn't significantly altered by an artist.