Last night I finished reading One Second After by WILLIAM R. FORSTCHEN. What a great novel. It follows a retired Army Colonel (R) turned history professor of a Christian community college in a small town just outside of Asheville, N. C.
One day everything stopped working at once. It later was determined that the cause was the detonation of nuclear bombs several miles above the earth's atmosphere. The resultant radiation causes a huge electromagnetic pulse to hit most the United States. The EMP knocks out everything that uses electricity or electronics. This includes all the electric appliances in the country, all communications, and most vehicles (only older engines would work).
The story then settles on how the people in this small town work to survive the resulting panic and dwindling food and medication supplies. The book is quite frightening in that thiscould really happen. If a terrorist cell could obtain just one nuclear warhead of the thousands that still exist from the Cold War stockpiles in both the U. S. and former U. S. S. R., it could be deployed from anywhere with a missle to detonate and trigger the Compton effect radiation that would cause such an EMP.
In the book, the United States is devastated by the breakdown of society caused by lack of food, medicine, and information. Society quickly degrades to a state of medieval state. I would suggest that you should read this book. It is available in print or ebook form. I just hope folks in our military are working on this possibility.