No it would also blow out transistors on every chip in every civilian electronics system. Cars might have some protection, because the under hood environment is pretty hostile to be with, electromagnetically speaking, although not at the levels of EMP. Ditto for electrical control systems, but less so. It's not just power systems that are affected. If you had line of sight to the blast, there is another effect called "TREE" transient radiation effects on electronics, which has to do with the prompt gamma rays from a nuclear burst causing transient effects in semiconductor materials, but high altitude EMP is more than just line of sight, because the electrons created by the gamma rays (actually knocked out of their parent atoms) move along lines of the earth's magnetic field, and can cause disruption over large (continent wide for a large explosion) areas. Even a "small" blast will cause EMP effects over a large area, just not so large or so severe as with a large bomb.
Were the Iranians, or another nation that had greater nuclear and missile capacity (like China or Russia), willing and able to explode an atomic device with the same power as the atomic bombs dropped on Hiroshima and Nagasaki 50 kilometers over Kansas City, for example, how widespread would the area affected by EMP be? Is there a formula that would determine what the effect would be in Kansas City, or in cities elsewhere in the United States?