I tried to look at the main documentation at http://graphics.pixar.com/usd/docs/index.html and http://graphics.pixar.com/usd/docs/Usdz-File-Format-Specification.html but cou
You can create usdz files online in a tool called Vectary:
Open Vectary editor.
Create your 3D model or import your 3D file with drag and drop (OBJ, STL, GLTF, DAE).
Export as USDZ 3D file in the right panel.
You will receive an email with a link to download your USDZ file.
More info on the url below:
https://www.vectary.com/3d-modeling-how-to/how-to-create-usdz-file-for-ar-online/
You don't need to rewrite the names of the object or materials, the tool does all the work.