The issue of EMP—Electro-Magnetic Pulse—has been around for decades. It wanes and waxes, but no one does much about the threat. Does anyone think the Department of Homeland Security is working this? At least not the Heritage Foundation folks, back in 2008. To be fair, DHS does list it as a factor under Nuclear Attack.
At any rate, since it is not just the threat of Iran or China popping a nuclear weapon 100 kilometers over the United States that we need to worry about. There is also the issue of "Space Weather" and EMP like action by the Sun.
In this article, from The Space Review, Yousaf M Butt talks about EMP, and promises us a second part.
Yes, the article is a bit on the Geeky side, but sorting past the deeper science those of us who are laymen can still get a sense of the problem. And, even if the CIA never does decide if Iran is building nuclear weapons, there is still the Sun out there to worry about.
Some are thinking about this, including Texas A&M.
Regards — Cliff