GFCI burned out during low transformer outage
A GFCI may look like an ordinary receptacle with a couple of extra buttons on it. But it is actually a sophisticated electronic device. Unlike many other devices (e.g., computer), it is run directly off of full main electric power, rather than having a large separate power supply that converts power to low voltage and can (and often do) take the "hit" and save the rest of the device from damage. Unlike many other devices (e.g., washing machine &amp; dryer, dishwasher, etc.) it is "always on", even if it isn't really doing much. In addition, the very nature of the GFCI is that it must monitor the electric current flowing through it in order to do its job.

As a result of all this, a GFCI is likely to be one of the most vulnerable devices to a severe overvoltage or voltage fluctuation event, which can happen with a transformer failure.

Fortunately, these types of events are relatively rare. Far more frequent are loss of power - either entirely (a blackout), to a limited degree (brownout) or a (typically) localized wiring problem (lost leg or lost neutral).

What can protect you from these problems? A whole house surge protector. This is typically installed at or near your main breaker panel. In a quick search, I could not find specifications as to specific voltage levels. They are generally for protection against nearby lightning strikes but can also help with utility problems and problems from interaction with other malfunctioning devices. I wouldn't consider a whole house surge protector an absolute guaranteed solution, but it should help mitigate the problem considerably.