An EMP, or electomagnetic pulse, can be caused by either a solar flare or man-made nuclear device. Either way, if the pulse is large enough, the effects - knocking out our power grids and burning out the transformers - could be catastrophic, possibly resulting in mass starvation. This article from NASA says the chances of solar EMP by 2020 are 12%.
According to this article, protecting our nation from the effects of an EMP would cost about $20 billion, which sounds like a lot, but certainly sounds worth the investment when compared to the potential consequences of doing nothing.
I think this is one time when all of us, regardless of our political affiliations, could agree that we should contact our local, state, and federal officials to demand immediate action. It doesn't take long to look up who your representatives are online and send them an email. If enough of us do it, they will pay attention and probably act on it.