The Z64 (USA) ROM has been preserved and emulated through various means, including:

The ROM's code reveals the early development hurdles of 3D gaming. n64decomp/sm64: A Super Mario 64 decompilation ... - GitHub 24 Aug 2019 —

use the USA ROM as a base to enable features like 4K resolution, 60 FPS interpolation, and widescreen support ROM Hacking : Major hacks, such as Mario Builder 64