simple noob question. If the TVS diode blows, it should short power to ground, correct? Now if power is an ATX PSU this SHOULD cause a overcurrent fault and power off the PSU???

This is just curiousity, so I understand things a little better, no data to be harmed, and no computers to catch on fire in case my understanding is wrong

IN THEORY and most of times it forces the PS to shutdown, on rare circumstances it doesn't power off , cabling and/or parts of the circuit overheat and there is a remote possibility of fire. Also, some cheap PS in this case try to compensate giving out much more than 5/12 with catastrophical outcome. That's it. If something CAN fail, sooner or later something happens.