The computer stops loading and waits for

The symptom you described happens because your printer is capable of reading memory cards.

When you turn on your pc with the USB cable connected, your pc is checking the memory card slots in your printer to see if any of them contain a valid operating system that can be used to boot the pc.

Once your pc determines the memory slots do not contain a bootable operating system, it then continues the boot process and loads the operating system from your hard drive.

When you disconnect the USB cable, the memory card slot are not present and the pc boots normally. I've run into this exact same situation at work with certain models of HP printers.

My best recommendation is to check the BIOS in your pc to see if it is possible to disable the option that allows your pc to boot from USB devices.

When you first turn on your pc, the screen will display a message informing you of which key to press to enter the setup program. This is where you want to check to see if the USB boot option can be turned off.
Note: Not all pc manufacturers provide an option to disable booting from USB devices.

If you can't disable the USB boot option, check to boot order to make sure the internal hard drive is listed before any USB devices.

I have to say though, setting the boot order so the internal hard drive appears before any USB devices does not always solve the problem even though it should.