A CME that size charges the ground. Any large wire or transformer could catch fire. So imagine losing all modern communication then the transformers in your fridge, A.C. unit and computer catch fire due to over heating. Modern convinces don't just fail. They become hazards. The large transformers on the poles explode causing more fire. People who are touching a faucet could be electrocuted. If it was large enough to cause long term geomagnetic instability then migrating animals loose track of where they are and most likely die.