Looking at the latest issue of the Bulletin of the Atomic Scientists (the guys that maintain the Doomsday Clock), I found this chilling map prepared by FEMA. It shows the amount of radiation expected to fall on the continental United States after a Soviet attack, by county. Look at how almost my entire home state of Missouri would have been reduced to a glowing cinder. Almost the entire state was classified as a Very High Risk area with exposure to over 15,000 roentgens. A dose of 500 roentgens for over 5 hours is lethal for humans.
In fact, the entire continental United States would have been subject to dangerously high amounts of radioactivity:
If the fallout levels that characterize a Low Risk Fallout area should occur, debilitating illness and possible death are certain for resident populations without adequate shelter.
Basically the entire population of the United States would be either dead or dying following a nuclear war and FEMA knew it. The only way to avoid it was to scurry underground into fallout shelters and stay there.