Re: *IF* these devices had decent replaceable or resettable fuses
Wouldn't work. Fuses protect against over-current conditions, like damaged cables. The USB Killer is an over-voltage surge. Fuses wouldn't do anything. Even if they could, their reaction time is on the order of hundreds of milliseconds - far too slow.
What you want to protect against this is a fast-response clamping diode. Transient suppression. Perfectly doable, but it'd raise costs, so it's not going to be something commonly found in consumer PCs. You might find it on PCs designed for industrial use, where harsh electrical conditions are more of a concern.