As I recall, Galileo (the European system) is designed to be interoperable w/ GPS.

More to the point, without direct knowledge, I can guess that satellites are hardened against EMP.

The problem is that EMP hardening is expensive. Ergo, a lot of stuff *not* spacebound is -not- hardened.

Launching to the altitude of the GPS satellites, also, is expensive (regardless of payload); The number of countries that can independently launch anything is small: 7 of them, and two (the UK and France) now combine their space operations under the ESA.

In short: Worry not about the satellites. They're safe from EMP. Worry about all the equipment that uses them. They're not.