Well, there are some problems with the physics of your statements. First, an EMP from a nuclear detonation is likely to generate ac fields in the EHF range. One component in the shunting ability of a faraday screen is wavelength, and the mesh size of a faraday screen determines the effective cutoff frequency efficiency of it's shunt. In short, unless your screen mesh size is approaching microscopic, it won't do much to protect against a nuke based emp.

Second, as the field intensity increases, the shunt capabilities of a faraday screen diminish because the ambient ground level goes up. Unless your ground plane is deep and is connected to the screen using massive conductors, the screen will develop a potential, or series of potentials that will induce fields in the equipment within. There are very few real true earth faraday screens in existence, at least ones capable of shunting major emp hits such as we are considering. Most faraday screens I know of are used to protect against lightning hit level emp. These can be big, but are localized and not nearly the magntiude a strategic emp attack would generate.

Third, cars are not grounded to earth, and therefore float on an insulating layer (four tires). They are not able to shunt an emf field at all, and provide virtually no protection to electronic gear contained within. To find a vehicle that would still run after an emp surge, it would have to have a generator instead of an alternator, because the diodes and the regulator in the alternator are semi-conductors and would be blown by an emp. You might get lucky and the battery would not take a hit, and the coil might not blow open, but anything silicon based is going to go after a few hundred electron volts. All those new LED lights everyone is toting these days will suddenly quit, leaving the good ole incandenscents. I dunno if the xenon and halogen lights will take the voltage or not, but my guess is certainly the new plasma based lights and the fluorescents are suspect.

Perhaps one of the smartest things I've ever heard about emp threat was to use tube technology and keep whatever appliance you were planning on using disassembled like a kit and packed away in an airtight aluminum container. If an emp hit, likely the componentry would survive intact, you could reassemble the unit, and assuming alignmnet was not a problem put it into operation. There are more than a couple dedicated ham operators and a few government agencies that subscribe to this practice.

The botom line is consumer electronics are going to toast in an emp field. Only the truly dedicated technicians who planned ahead have any chance of operating electrical gear after the fact, and even then, they're going to have to come up with suitable electrical generating devices (you can pretty much say goodbye to all those new portable generators too, which are dynamically controlled with solid state electronics).

Just enclosing equipment in a metal structure will not keep it safe. I've witnessed a lightning strike take out a telco switch station from 1/4 mile away. This was a site that was in a metal building, with a good grounding system, and plenty of circuit protection. If it can happen to a $50k switch site, then it can happen just about anywhere.