Re: *IF* these devices had decent replaceable or resettable fuses
Transient suppression. Perfectly doable
Up to a point. TVS devices are rated for some amount of energy; exceed that and THEY blow up (plus the hardware it's supposed to protect). So whatever your TVS rating is, there'll always be a zapper that can put more energy into the protection circuitry than what it can handle. Although in the case of an USB killer you'll then be seeing devices that have to be a good bit larger than the average thumbdrive, so maybe the unwary finder of one of those wouldn't put one into their PC rightaway.