True. But detonate it over Pittsburg and you would wipe out the entire grid east of the Mississippi River and affect the majority of Americans.
30 miles over Pittsburgh, at the top of the stratosphere, way above where planes fly, past the reach of high altitude balloons. The math just isn’t there. Look at that map with the circles again and the altitudes involved, the small circle is for an altitude higher than the best high altitude balloon can get to by about 1/5 of their capability, the biggest circle is almost 20 miles ABOVE the international space station. Who’s getting nukes up there? We aren’t even getting nukes up that high.