“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
Prior to Trump and his saboteurs getting into office, US grid operators were pretty good at planning for these events.