Not really.
A Calculation Model for High Altitude EMP
Double digit megaton warheads are not efficient at all. Clusters of smaller nukes are the better method. And you'd need a lot of them to blanket the US with sufficient EMP to mess up the bulk of the consumer electronics across the entire US.
That's very true. There's a reverse curve in Megatonnage to EMP and direct thermal/blast effects. A 100Mt bomb is not 200% more destructive than a 50Mt device.
Larger weapons are also
exponentially more expensive to produce, and there's increased maintenance and a shelf-life on some of the isotopes and "special herbs and spices" the larger devices need (especially if you're trying to make it compact as possible). And designing them to optimize EMP effects vs. blast/thermal output adds a whole other layer of complexity. Despite the fact that we made the first fission bombs in 1945, North Korea's recent underground sub-kiloton "fizzle" proves that even the most basic gun-barrel or sub-critical Uranium devices still aren't "easy", even for an entire nation-state, one presumably with access to "axis of evil", Bill Clinton, and other assistance.
And it's true there are capacitor/coil/conventional explosive EMP devices, but they're not "easy" either. There's a reason the U.S. and other top-tier militaries are the one's experimenting with them, and only within the past decade or so. Like the nukes, the basic theory is out there for anyone willing to read PopSci, but like any complex undertaking, "the devil is in the details", and that's the stuff that's kept truly under wraps by the first nuclear powers.
Then, even if you have achieved a multi-megaton capability, there's the size/weight issue to contend with, what that does to the range or capabilities of your missile, or if a whole new multi-year program is needed to develop a new launcher.
It's not as simple as assuming that the U.S. and USSR were "doing this" in the 1950's/60's, so 2000's era rouge states can do it now. These are exponentially expanding technical challenges, it's not a linear progression. (And Russia had lots of help in the 50's and 60's due to espionage in America to get their program jump-started...) And the things you expect to help, like cheap pervasive and powerful computing do help, but not to the degree people would automatically assume. There's whole entire industries that need to be leveraged, materials science, ultra-precision machining, metallurgy, electronics, chemistry etc. You have to be the best and have the best in all of them, or it's going to slow your program down. There's still a lot of hard-won technical knowledge and methods we've had since the 40's that are still not public domain.
For the next decade or two at least, an EMP attack is only a threat from Russia and China. Container ship or van-delivered ground-bursts are probably a threat now.
The Iranian scenario as posited in the WSJ article is troubling and has some true potential for direct attack, but even if they had the EMP capability to blanket the entire U.S., my gut tells me they'd prefer a direct strike. It seems to me that the Islamists prefer fire, body count, and destruction.
