Except there are several problems with this. For one, the batteries in a walkie talkie are different from those in other devices. We dont know how different batteries are affected. Additionally, the motorcycle requires electronics to start. A battery and electrical wiring etc. There are also lots of devices that can record video without a battery. My laptop can be plugged in without the battery inserted. And on top of that, murphys radio proves that electronic devices were not totally wiped out. Her radio worked, and long enough between battery swaps to be tactically useful.
There is also the glaring issue of the attack choppers. Those things are full of electronics required for function, both in the weapons and for flying. They are basically flying computers. Those worked but I am supposed to believe that no one got footage of the attack? Rubbish.
The Formor literally discussed the arrival of the "mechanical weapons" of the NG arriving. They discussed it as a matter of concern, so clearly they were also not confident that if they were still fighting by the time the NG arrived that the magical energy present would somehow save them.
It's not just batteries. Guns jam. Motors break. It's just that electronic equipment seems to be more susceptible. So even non-battery operated equipment is going to break.
As for the choppers, they came in from outside the affected area. That's why it took so long. Anything close to Chicago was fried. When on the boat, I think he commented that the waterfront was dark, and only the distant light from Aurora (42 miles west of chicago, an hour commute) were visible on the cloud cover.
(Admittedly it shouldn't have taken all night for the Guard to get there, but that's another argument)
The best bet is that those in the know in the government guessed what was happening, and had the Guard hold off until morning because anything sooner might be just wasting assets.
The Librarians will secure and recordings from the Guard, and anything that goes public will disappear in short order.
The thing is, none of us are arguing that things won't be changed and the local public won't know. We're arguing that there won't be overwhelming evidence of what happened. Conspiracy theorists will spread the word, but the rest of the country and the world will fall in line with the official story.