As an amateur radio operator, The high bands get wiped first! 80, 160, not so much (no ionosphere? ground wave still works. Easy to throw up a long wire … afterward). Hams (esp. ARES) will become VERY IMPORTANT for a LONG time when it happens. Field Day is a good way to prep for aftermath. (Gear can go into metal containers to escape parts damage until afterward.) Portable generators (best without a lot of electronics on them) will be needed to re-charge the batteries!

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).