Total BS
a) Umpteen different hams across the country would have had to have heard the 'report' (the massive click) over the HF/SW bands up into the VHF freq range - aircraft radios, which utilize amplitude modulation would have also have had their carrier-level actuated squelch circuits 'opened' with a large burst of noise (all these people would eventually pool their knowledge and compare notes - as we are like to do to find out where various anomolies origonated)
b) radios and televisions in the area would have been harmed - giving as CLEAR indication of the area where such a device was used based on the extent of damage
c) Too damn much evidence to the contrary - instrumentation in substations, generating stations, et cetera, that indicates a progression of events over, well, as much as an hour before including the four tree-contact events ... an EMP device would have been all-at-once (relative to an hour or even a minute) release of energy ...