Hi Bill,
The main role of the breaker is to protect the downstream wiring in the case of overload caused by malfunction of downstream devices/wiring and thus prevent fires. Not so much the person or the equipment. Read up on GFCI receptacles if the mood strikes you for info on that. Excessive sustained current draw downstream (ie beyond that of the breakers rating) will (should) trigger it to discontinue passing AC to the downstream wiring.
The breaker will be the first to see the spike of current coming from upstream (lightning etc) but may not and often does not respond quickly enough to save equipment (not its design criteria) and likely will not respond at all, at least in any effective way. Thus the importance of faster and more reliable protection devices in the AC link downstream but prior to the audio equipment if incoming surge is a concern. By and large, if these devices use MOVs/chokes, etc. as the sole method of protection, they will do little to protect equipment anyway in the event of an extreme surge on the incoming AC line. $$ "guarantees" are a cruel joke and an indicator of an inferior and incapable product from a company that prioritizes marketing over performance.. Much to be read on the WWW re: the Monster "guarantee" and the weasel words deliberately inserted by their legal team to avoid any type of compensation actually being rendered. Look inside the device for the real story of its value in protecting audio equipment or especially in improving sound quality. If you see "lollipops" (MOVs) and chokes, recommend that you MOVe on to a real product that uses modern and superior technologies that actually work. They usually cost money.
In 30 years of audio, I have only had one component (a TV) damaged by lightning surge and that came in through the cable provider’s RG6 line, not the AC, in an apartment complex. Learned that devices that effectively shield the equipment from incoming TV cable problems are more valuable than the AC-only type.
My power conditioning products over the past 10 years do not contain components for surge protection in the interest of better sound quality. I live in severe-thunderstorm Hades (near Houston) so admit to being a risk taker. So far, so good.
Dave