Clinton knew, as did all the presidents following him. What has been done about it? Not much.
The danger of an EMP has been known for a long, long time:
Nuclear electromagnetic pulse | physics | Britannica
https://www.britannica.com/science/nuclear-electromagnetic-pulse
...in 1962 a failure of electronic components in street lights in Hawaii and the activation of numerous automobile burglar alarms in Honolulu were attributed to a high-altitude U.S. nuclear test at Johnston Atoll, some 1,300 km (800 miles) to the southwest.
nuclear electromagnetic pulse (EMP)
a time-varying electromagnetic radiation resulting from a nuclear explosion. For a high-yield explosion of approximately 10 megatons detonated 320 km (200 miles) above the centre of the continental United States, almost the entire country, as well as parts of Mexico and Canada, would be affected by EMP—destroying practically all electronic devices and electrical transformers. Procedures to improve the ability of networks, especially military command and control systems, to withstand EMP are known as “hardening.”
