What is the risk of an electromagnetic pulse attack?

There seems to be 2 trains of thought in the US--(1) yes, this is a serious security threat to our country and we are almost totally unprepared of (2) the likelihood of an EMP attack is low as it would be very expensive to obtain, test, etc. and this would be the least of our worries--if a terrorist group or rogue state got ahold of a nuclear warhead (detonated at a high altitude would cause the EMP attack), we would have much larger public safety concerns.
You are probably right--this is not the correct forum to start a dialogue on this issue. Thanks for your response.