The attack involves taking down a high-value system via low-value, readily accessible USB port.

I imagine that the USB PHY of a well designed system exposed to this attack will not survive, but the entire system won't be so easily nerfed either.

Except the PCH usually contains the USB PHY and when the PHY dies it takes the PCH with it.

Or wire your USB plug up to a 120/240v power plug?

That is remarkably close to what this thing does.