What are the US laws regarding derived content?

Question

In other words, is it legal for me to take a photograph and edit it beyond recognition?

Answer 1

if you took the photograph with your camera, or licensed it for those purposes, yes.

otherwise it is a derived work, subject to copyright sanctions.

Answer 2

If it is truly "beyond recognition" then from a practical standpoint you are clear because the copyright owner would have to recognize that you used their content and be able to prove it in court.