First of all. To get EMP you need to detonate in the atmosphere. High up to be sure, but it is the interaction with the atmosphere that creates EMP. Too high and all you have is xrays and high energy particles, so only close stuff is affected. In space a mile wide killzone is in fact really small.
Secondly EMP is *not* the end and is not even that bad (don't believe the movie bullshit). It is like the opposite of a geomagnetic storm. Large power infrastructure is mostly unaffected. Small electronics close to the epicenter *and* turned on will be affected worse. However even civilian electronics tends to be fairly well shielded and even on substrates that give quite a bit of resistance to the pulse these days. Also some stuff will just need to be power cycled. But yea there would a bit of stuff that wouldn't turn on anymore. However hardly the end of the world.
An air burst however would be far far worse.