In January, 2001, A commission chaired by Donald Rumsfeld released a report to Congress regarding the vulnerability of U.S. satellites.
I agree that our nuclear stockpile is an excellent deterant. But here's the $64,000 question: Would an attack on our communications network be considered, by whatever administration is in office at the time, this as something that demands a nuclear response? We may have a limited missle defense operational at that time but China may be able to get a couple of birds past it. At this point China is glowing, cratered, radio-active wasteland that no longer has an over-population problem. Gravel from California is pelting Nevada, New Mexico and Oregon. NORAD is scrambling to re-establish communications that were cut off after 90% of U.S. satellites went silent. When the communication satellites went down, the Internet and telephone networks across the country are overwhelmed within minutes. The loss of the GPS satellites add to the communications problem because long-distance and local switches operated by US telecom carriers rely on the GPS network for a timing reference to synchronize their their networks. While all of this is happening, Russia is becoming a little more than upset about the dozen 10 megaton warheads raining down from the heavens so close to their back yard......Well, that's my version of a possible worst case situation. Since you actually served in SAC, I imagine that you would have a more accurate picture of the players and what level of threat they pose to us.
No, it won't happen because their chances of ultimate success are slim to zilch and the risks FAR outweigh any potential gain.
As to the (very good) question you posed: would a launch of such "EMP birds" over our country result in a nuke response? Yes. Absolutely. We won't wait 'round to determine what kinds of birds they've lobbed our way. That is a fact.........and we'd know where they're headed the minute they've launched.