“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
There are A LOT of BIG countries with big electric grids in the world today. Which countries GRIDS get hit the worst depends on which side of the Earth is facing the ‘hit’. Could the West (US, Brazil) or Europe or the East (China, India).