1) To reiterate the basics, the primary concern with a nuclear attack on the USA is fallout — since the other major effects of nuclear bombs (blast, thermal radiation,etc) are relatively limited in extent.
You are probably safe if you are 8+ miles upwind from a nuclear detonation of 1 MT  or less, provided you don’t blind yourself by looking directly at the nuclear detonation. Fallout, moreover, is generated by nuclear strikes at ground level. But many nuclear detonations would be made 4000 feet above a target [“air bursts”]– in order to maximize the blast effect — and such air bursts do not generate fallout to any significant extent.
1) The highest priority targets for nuclear strikes on the continental United States are our Minuteman ICBM  sites. (In order to reduce the damage from our counterattack.) Unfortunately, however, such an attack would generate massive fallout clouds because of the need for hundreds of ground strikes to destroy hundreds of underground Minuteman silos.
(Note that only Russia has the forces to mount such an attack — I believe China only has roughly 15 ICBMs. Note also that Russia’s missile forces are declining.)
Your blog entry of January 16, 2006 had a link to a report from Nukewatch which noted that our Minuteman sites are being reduced from 1000 missiles to 500 missiles. Note, however, that the remaining
500 missiles will continue to be deployed in the three existing Minuteman “nests” [a.k.a. “missile fields”] around Minot Air Force Base (AFB ), (Minot, North Dakota), Malmstrom AFB (Great Falls, Montana) and F.E. Warren AFB, (Cheyenne, Wyoming).
2) Each of those three nests cover an area roughly 60 miles by 100 miles around the commanding AFB, as shown in the three maps in the Nukewatch report to which you linked .
It would still take hundreds of ground strikes to reduce each nest–which would still result in huge fallout plumes reaching to the East Coast.
See the FEMA 196 map  — these major fallout plumes are shown in red.
Since the three decommissioned Minuteman nests were the easternmost of the sites, then the length of the major fallout plumes (shown in red on the FEMA 196 map) would shrink toward the west. For example, since the fallout plume from Minot AFB, North Dakota would no longer be enlarged by the plume from the decommissioned Minuteman nest in Grand Forks, North Dakota, then the major fallout section of the Minot plume (shown in red on the FEMA 196 map ) would probably reach only to western Michigan vice upstate New York. Note that upstate New York would still receive some fallout from Minot but it would be at more moderate levels (yellow shading vice red on the FEMA map.) Similarly, the red plume from Malmstrom AFB (Great Falls, Montana) would probably only reach to Iowa (vice western Pennsylvania as shown on the FEMA 196 map) , since it would no longer be enlarged by the plume from the decommissioned Minuteman site around Rapid City, South Dakota. Finally, the red plume from F.E. Warren AFB (Cheyenne, Wyoming) would probably reach only to western Kentucky (vice New York City) because it would no longer be expanded by the plume from the decommissioned missle nest in Missouri. So the net effect of the Minuteman cutbacks is to lower the fallout expected to be deposit on West Virginia, Virginia, and Pennsylvania. Surprising, huge classified bunkers intended to shelter government leaders have been publicly exposed in that area: Mount Weather in Berryville, Virginia. Raven Rock in Pennsylvania. The Congressional refuge under the Greenbriar Hotel in West Virginia. (Only our esteemed political leaders would put a shelter for global nuclear war under a five star hotel.) It is the fallout clouds [kicked up by grround bursts] that make survival in the states east of Montana-Wyoming-Colorado and north of latitude 36 degrees problematical.
Note moreover that daily shifts in the jet stream affect where those fallout plumes would be deposited . For example, Today’s map of the stream indicates that much of the fallout from a strike on the F.E. Warren AFB nest –if the attack were made today — would be deposited on Oklahoma and eastern Texas, rather than toward the east as shown on the FEMA  196 map.
3) What has changed since FEMA 196 is that missile nests in Missouri, South Dakota, and Grand Forks, North Dakota have been decommissioned. This would cut the size of the major fallout plumes (shown in red on the FEMA 196 map ) by roughly half.
The locations of both the active and decommissioned Minuteman nests in the above states can be seen by going here and selecting one of the “Dense Pack” states (shown in red) 
4) Some of your readers have suggested that targets with economic value (oil refining area, cities,etc.) will be hit with air bursts or neutron weapons in order to kill people but save material. As I noted,
Little to no fallout is generated by such attacks. But I think it more likely that Russia would hit many of our cities with ground bursts in order to generate fallout. That would deny those economic resources to US survivors in order to prevent America from recovering and ever becoming a future threat. So probably the East Coast from Norfolk, Virginia north to Portsmouth, New Hampshire and 100 miles inland would be in trouble even without the massive fallout plumes from the three Minuteman nests. As would the areas immediately east of the major West Coast cites.
5) There are many other point targets (e.g., airports with runways strong enough to handle B-52s ). As I noted earlier, for any one such target, you are probably safe if you are 8+ miles upwind from
the target. If you are downwind from one or more targets for which ground strikes are likely, then you have to estimate the likely fallout plumes, amount of deposited radiation at your location,
and the amount of fallout shelter you will have.
6) But fallout would also kill off wildlife and many farm animals. Plus even mild nuclear winter would hurt crops, as we’ve seen in past eruptions of volcanoes. Moreover, much of the massive fallout from an attack on the Minuteman nests would cover the prime food growing areas of the Midwest. So famine would be likely. As you have noted, the high population density in states east of the Mississippi would make survival difficult. – Don W.