If you can boot off a USB drive, and the USB you have is a Windows 10 System Repair disc or can create one, or you have one of those, you would probably have been able to run a Windows Repair and get everything back as it was. This is the easiest thing to do when Windows gets broken and you can't boot. I make a current Windows System Repair disc (DVD) about once a year, so that the environment is up to date. You made one, didn't you?
It is a bit hidden in Windows 10, and actually uses the Windows 7 Backup and Restore functionality, but it is supported and works. Windows Settings > Update and security > Backup > Go to Backup and Restore (Windows 7) > Create a system repair disc.
I think you can also download an image of a recovery environment disc from Microsoft somewhere, if you don't have such a disc already. Google is your friend. Make sure you get any such environment from a legitimate source.
PS: Not to forget, depending on where you got your PC and how it was setup, there may be a recovery environment on the hard disk. You just need to work out how to initiate it. Usually a key combination or through BIOS. You may also have been able to boot to Safe Mode and fix the issue. Lots of ways to fix these things other than rebuilding Windows.
https://www.digitalcitizen.life/4-ways-boot-safe-mode-windows-10