Actually, that's a pretty horrendous common mistake. The maximum of the blast radius of every nuclear warhead is below 50 miles. The biggest one ever designed,

Actually, that's a pretty horrendous common mistake. The maximum of the blast radius of every nuclear warhead is below 50 miles. The biggest one ever designed, but not tested, by the USSR (larger than the US) was 100 MT which would've had a blast radius (third degree burns) of 46.5 miles, if it was detonated at 50,000ft , less with lower heights. That is a far cry from "within a few hundred miles".