“The exercise was held from May 8 to 9, 2024, at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, and at a Federal Emergency Management Agency (FEMA) site in Denver, Colorado.”
Article refers to a PDF of the report it’s based on:
https://www.jhuapl.edu/sites/default/files/2025-04/Space-Weather-TTX-Report-Summary-v3-FINAL.pdf
At that point, that grid connection will be the least of anyone’s worries. The storm in Quebec in… 1990? Ish. tripped breakers, and shut things down for like a day.
A storm on the scale youre talking about I am pretty sure would wipe out satellites (maybe even take them down due to atmospheric drag?), impact cables other than power like copper laid for internet and phone, etc. Grid-connected power or not you’d be severely impacted and potentially at risk.
Oh yeah, a large enough solar mass ejection in such a direction that it would directly hit planet Earth would be extremely bad.