About the Russian EMP threat against the United States: There have been several reports that in 1999, a threat was made by Vladimir Lukin, who was the chairman of the Russian Dumas International Affairs Committee. That position is similar to the chairman of the United States Senate Foreign Relations Committee.
Lukin told a United States Congressional delegation that if NATO forces didn't get out of the former Yugoslavia, then Russia could, without fear of retaliation, launch a missile from a submarine, explode it high over the United States and shut down our power grid and communications for 6 months.
Vladimir Lukin was probably bluffing. I don't think that they would have actually taken such a drastic action in that instance. Russia clearly, though, wanted to communicate to the United States that they had the ability to flip a giant ON/OFF switch controlling the United States to the OFF position.
It certainly did scare the U.S. congressmen who heard him make the threat.