Popular Science had an article on how to build a conventional explosive EMP. A person could probably wipe out a city. There was discussion that older vehicles might now be be damaged. The hood could shelter some of the ignition electronics.
As little as a year ago I didn’t think an EMP was anything to worry about, but lately, with the increase in cyber-terorrism, ISIS (where are they getting their funding? could they be used as a proxy to attack the U.S.? Clearly, they couldn’t care less about destroying The Great Satan), and then the news item about Cheyenne Mountain being re-opened to store vehicles, etc. from EMP ... I’m not quite as nonchalant about this threat.