Pretty sure it’d fry the power supply. Thats my first bet, is that it wouldn’t even get through it.

If it did pass through, it could fry your electronics. A USB killer is a short pulse, and not at all strong compared to main, so I expect that it’d act more like if a neutral was floating, than an actual surge at the voltage a USB killer usually gets to.

No idea for sure though and I’m not an electrician.