EMP has been know about since the 1950's but unless a nation has an ICBM, there is no way to get a nuclear warhead over the United States high enough to create a continent wide EMP. Also, you would need a very large device, well into the megaton range to do significant damage. Iran doesn't have an ICBM nor do they have a thermonuclear weapon.
Cool. I bet Iran would be willing to push the button, if they were given the assets...
>EMP has been know about since the 1950's but unless a nation has an ICBM, there is no way to get a nuclear warhead over the United States high enough to create a continent wide EMP.
The United States is not Iran's enemy - Israel is. Not only is Israel their number one enemy, but it's also an easier target.
Iran is bluffing. If they had the capability they would have used it long ago.