Maybe
Your troubleshooting was BRILLIANT! Running from the external hard drive and comparing the two really helps. Obviously, there's something different between the two PC's. Maybe the graphics card? You have a 1060, right? I think your install log showed you have DX12; I wonder if SimCity is having an issue with it. Have you ever tried creating a profile for SimCity in NVidia GeForce Experience?
*edit: after all the install-reinstall, it probably should have installed the correct DX version for the game, but you could try a re-installation anyway. Run DXSetup (as administrator) from \Program Files (x86)\Origin Games\SimCity\__Installer\directx\redist