With current technology, you'd be hard pressed to create any single EMP device that had a range exceeding a few dozen kilometers.

How about a 50-year-old technology?

"In July 1962, a 1.44 megaton (≈ 6.0 PJ) United States nuclear test in space, 400 kilometres (250 mi) above the mid-Pacific Ocean, called the Starfish Prime test, demonstrated to nuclear scientists that the magnitude and effects of a high-altitude nuclear explosion were much larger than had been previously calculated. Starfish Prime made those effects known to the public by causing electrical damage in Hawaii, about 1,445 kilometres (898 mi) away from the detonation point, knocking out about 300 streetlights, setting off numerous burglar alarms and damaging a microwave link." Source