Both of you are correct. A low-level nuke explosion maximizes damage, but EMP is inherent in a nuke and is more effective the farther up it goes bang (depending on its power). The idea of using one at higher altitude to blow everything electronic and return the target, in this case America, to the 1800s has been around since the cold war. As the most electronically dependent major power, we're the most vulnerable. So the Iranians have been working on short-range delivery systems and doing test explosions (conventional for now) at altitude, which I'd suspect would be primarily aimed at knocking out defenses of our military in the Middle East, and also that of Israel. It could do some serious damage here if they have strategic launch points, but a comprehensive knockout hit would more likely have to come from their recent ally, Russia. The threat has been around for decades. This is just the latest on it. I think I wanna live underground. I think I want my garage underground. Am I paranoid now? Shhh. They might hear.
Here's a congressional hearing from four years ago that relates:
http://commdocs.house.gov/comm...0.HTM