“You need very long conductors in order to be effected by the magnetic field. Hence the power grid is pretty much the only thing in danger.”
The conductors of the power grid do not in any meaningful way couple to geomagnetic field variations.
What happens is that the variations penetrate deep into the earth, inducing currents which can make the ground potential between two geographically distant substations to vary significantly. This causes currents to flow between them and if the currents flow through a transformer, it can under certain conditions destroy it.
That’s how a solar storm impacts the power grid (or pipelines....or...)
Yeah I though of a couple more. Copper phone landlines and cable TV lines.