Asteroids can theoretically be deflected.

Solar flairs and EMP could theoretically be hardened against (though it is unlikely that personal devices could be and everyone's cell phones not working would likely be more damaging to society than a zombie outbreak, or at least would look a lot like one with 90% of the population wandering aimlessly hunched over looking at a blank screen).

The impact on the food supply to the world, both from the destruction of one of the largest single producing areas (Midwest US) and the impact of the mass ash release would be nearly impossible to protect against.

The Irony is that the part of the US that we all assume would fall off into the ocean one day would be least impacted as the prevailing winds push the ash cloud east. Of course they would have no water or electricity since they get most of that from points east.