IIRC the Whitney Streiber book “Warday” covered this scenario quite extensively. The depression caused by loss of currency in electronic tranit was the most significant result as well as the physical destruction caused by the relatively few warheads that were able to reach their targets after the EMP was set off. In that story, the US and Soviet (yes, it predates the breakup of the USSR) EMP weapons were hidden in satellites that were able to maneuver over the target countries and eject their weapons.
Really, really good book.
I found it hard to believe that it was the same Whitley Streiber that wrote “Communion”.