.... The protection diodes found within the USB host are only designed for ESD-like voltages and currents. They can not handle a high voltage being applied for a long time.
Electrostatic Discharge can be around 20,000 volts. What do you think makes the spark and the "snap" sound?
But it might be shorter than this thing, it depends on how big the caps are. And how long the devices can endure the overage.