Is there a way to modify usdz file directly or be able to convert it to obj file so that it can be modified? I don't have original 3D file so the 3D tools doesn't let me import it at all? Any help is much appreciated. Thanks!
If you drag a usdz into xcode you can convert it to a .scn by following these steps:
I think you could also create your own conversion tool (macOS app) using Apple's Model I/O framework so you could convert from USDZ to OBJ.