Based on the wind direction that day, and the fallout patterns from similar-sized Castle Bravo test, here's a map:
https://www.google.com/maps/d/viewer?msa=0&ie=UTF&mid=1MhXe2hTJpUmVg3n5CgCDidvjbwo
- The Clintons would be safe in Little Rock. Mondale's plane was already out of the blast area by the time of the incident.
Quick summary: America is screwed, worse than Russia after Chernobyl.
- Several thousand people die that night; and millions more (including the entire Fayetteville, Wichita and Tulsa metro areas) will be forced to abandon their homes and businesses forever. This includes Sam Walton; there will not be Walmart.
(Abandoned stretch of I-44, inside "Pink Zone" northeast of Tulsa. Note dead/dying vegetation.)
- A huge exclusion zone has to be drawn right across America's breadbasket.
- Carter will of course stop campaigning. Reagan wins (even though he also suspends his campaign) but it's a hollow victory. In OTL, Reagan's tax cuts and spending increases took nearly three years to bring about a recovery (if in fact they were responsible). He probably won't get that sort of blank check in this scenario; and he'll be lucky to get re-elected at all.
- Even in 1980 dollars, the damages would be in the hundreds of billions. We have to relocate millions of people, re-route I-35, I-44 and I-40, and have USDA agents inspecting every gallon of milk sold in the USA with Geiger counters. Ditto every used car, washing machine, etc. to make sure they're not stolen and contaminated. Radio Shack sells a LOT of Geiger counters.
- So, there's not going to be a Reagan Recovery, nor a big increase in military spending anytime in the 80's. Besides the huge economic hit, it will be politically impossible to put Pershing-II's in Europe. All Titan-II's and B-53 bombs in our arsenal will need to be taken offline as well, while a Congressional committee (headed by Richard Feynman) tries to figure out how the hell this happened. There will be a great deal of political pressure to unilaterally disarm.
- By examining satellite photos of the crater size, the Soviets are going to figure out that a well-known formula (in Glasstone's 1977 book) for yield-vs-crater depth is wrong, and that our existing warheads probably can't take out their buried command-and-control bunkers.
- Bottom line: we end up with a second Great Depression, and a new phase of the Cold War where we're stuck at post-Vietnam levels of funding, AND can't use nuclear weapons to deter the Red Army. No "Morning in America", and "Red Dawn" might actually be plausible.