1 megaton at an altitude of 48 miles (if I remember correctly) over the center of the midwest US will create a strong pulse that will cover the entire US of A.

1 megaton exploded at 10,000 ft over a city will have a 10 - 20 mile blast effect. It will have a fallout footprint of 30 miles upwind, 50 miles cross axis, and 350 miles downwind. Hills and mountains will deflect the blast waves and affect the wind patterns irt fallout and the wind that will draw oxygen into the NuDet. Nagasaki, Japan was a good example of this.

The type of material (weight) will greatly affect the Fallout Footprint. The greater amount of radioactive particles that are blown into the upper atmosphere, will be inert (radioisotope) when they come back down to earth.

There is an EMP map that can be found at www.standeyo.com
That article came out last month so you may have to search the archives to find it.