These threads are always frustrating, because they always turn into a debate of whether there will be a situation in which all electronic devices are rendered inoperable, or whether such a situation will never take place.
As with any natural or manmade phenomenon, the real issue isn't that black and white.
EMP is electromagnetic pulse, which could be caused by a number of things. Most commonly, we think in terms of it being caused by a very high altitude nuclear blast. It is an very strong electomagnetic field that lasts for a very short period of time.
Electromagnetic fields are all around us all the time, in the form of radio waves. A very high altitude nuclear blast would cause an extremely strong electomagnetic field, which would be very strong over a very large area. Other possible EMP weapons would cause a very strong electromagnetic field over a much smaller area. Solar phenomenona might cause similar effects over a large area.
But EMP will have negative effects because of the strength of the field in a given place, not merely because of the existence of the field somewhere. Again, electromagentic fields are all around us. At some point, if they become strong enough, they will cause damage to various items.
To give an example, wind can cause damage to things. If the wind is 1 MPH, it probably won't cause very much damage. If it's 30 MPH, it might tip over the garbage can. If it's 50 MPH, it might blow off some shingles. If it's 100 MPH, it might break some windows. If it's over 100 MPH, it might cause the whole house to blow down. The strength of the wind is what causes the damage, and the amount of damage it does will vary depending on the strength.
The same is true of EMP. Again, we already live in an environment of electromagnetic fields. You could think of it as a gentle 1 MPH breeze.
You could think of EMP as a 100 MPH wind. (I should note that the actual strength of an EMP would be many times more than 100 times stronger than normal electromagnetic field levels.) But it wouldn't necessarily be a 100 MPH wind everywhere. For example, an "EMP weapon" (as opposed to a high altitude nuclear blast) would have very localized effects. 20 miles away, the EMP wind would be a normal 1 MPH.
For a high-altitude nuclear blast, the area of 100 MPH wind would cover a finite, albeit large, area. As with any wave, the intensity at a given area is governed by the inverse square law. This means that if you are twice as far away, the effect is 1/4 as strong. If you are 3 times as far away, the effect is 1/9 as strong.
Now, this is somewhat complicated by the fact that the origin of the EMP is not a single point, but acually an area within the earth's magnetosphere. But still, that's a finite area, so the inverse square law means that the effect will be diminished as you spread out.
So let's assume that 500 miles from the center of the area affected by the EMP, the EMP is like a 100 MPH wind. If that is true, then 1000 miles away, the EMP is like a 25 MPH wind. And 1500 miles away, it is like an 11 MPH wind.
Two things stand to reason: The first is that there will probably be less damage from the 11 MPH wind than there is from the 100 MPH wind. And the second is that there are probably a small number of very sensitive devices that will be damaged even by the 11 MPH wind.
But it's not an either-or proposition. The question is not whether everything will be destroyed or whether everything will be fine. The actual question is how great the damage will be.
The sole practical experiment that was ever conducted involving EMP caused by high altitude nuclear blasts was during tests in the Pacific. There was some unanticipated damage in Hawaii (which is basically how the phenomenon was discovered). However, all electronic devices in Hawaii were not destroyed.
My belief is that in a plausible high-altitude nuclear blast over North America, power will be out over a large part of the continent. This is because even if a relatively small percentage of the components in the power grid fail at the same moment, there will probably be cascading failures of other items. It seems to me that the immediate effects would be almost the same, whether 1% of the components on the grid failed, or whether 90% of them failed. Either way, it seems to me, there would be an immediate failure. Of course, if it's 1%, then it's probably easier to effect repairs, and power might start functioning in some areas quite soon. If it's 90% of the grid that's damaged, then it might take a lot longer.
I think the risk to individual electronic devices that are disconnected and not in use is very low, close to zero in most areas.
This is largely academic if we're merely discussing whether life will go on as normal. Such a widespread power outage, even if corrected fairly quickly (which is somewhat unlikely), would mean that normal chains of distribution of fuel, etc., would be very unreliable for a long time. In short, it's quite likely that your car would start just fine, but fuel won't be available, and you probably won't have anyplace to drive anyway. So IMHO, it's largely academic, if we're just thinking in terms of life getting back to normal. It won't be normal, even if damage is minimal, IMHO.
It becomes less academic when we think in terms of personal disaster preparations. Many electronic devices are important to personal preparations, and these are devices one might want to use, even in the absence of a national grid. For example, you won't need your car to drive to work, because it's unlikely that you'll be going to work. But if you need the engine in the car to generate electricity or conduct mechanized agriculture, then it's a different story. And you won't be surfing the internet with your computer, because even if the internet is out there somewhere, the routers and lines between you and the outside world probably won't be functioning. But you might need data stored on a computer (although frankly, I think it's imprudent to store important information in this manner). And you won't be listening to the top 40 on your radio, because the remaining radio stations will probably have more important things to talk about. But having a radio to listen to those remaining stations could be critical.
It seems likely to me that most of these discrete devices would remain functional. This is especially true if they are unplugged at the time of the EMP event. And this is almost certianly true if even a little bit of thought is given to how they are stored.
Personally, after an EMP event, I will almost certainly be listening to the radio, and I will also be transmitting. Chances are, the normal radios that are plugged in right now will work fine (once I put batteries in them). If not, I have plenty that are stored away, with varying levels of protection. Since I doubt if there will be power available, I have plans for producing the small amount of power that I will need.
Almost as certainly, I will not be using any computer. This is not because the computer will be damaged. It might be, but I really don't care. For my purposes, using a computer would be a waste of very precious electricity, without much benefit. So for that reason, I'm really not planning on doing any post-EMP computing.
Similarly, it's very certain that I won't be using any vehicles, at least not very much. This is not because I think my cars will be damaged. They might be, but I really don't care. Again, for my purposes, using a car for transportation would be a waste of very precious fuel, without much benefit. So for that reason, I'm really not planning on any post-EMP vehicle use.
This would obviously be very different if I were, for example, a farmer. In that case, having the use of at least some machinery would be vital to not only my survival, but the nation's survival as well. So in that case, I think I would take some precautions to make sure that some vehicles and machinery were hardened, or at least were such that they could easily be repaired.
Again, EMP is not a magic bullet that will either destroy all electronics, or leave all electronics unscathed. As with everything, we have to recognize that there is a certain level of uncertainty, and focus our preparations where they will have the most potential benefit.