EMP’s can be man-made or of solar origin. An enemy could explode a nuclear weapon hundreds of miles in the atmosphere over the continental U.S. Any circuitry in a direct line of sight from the detonation could be taken out through this pulse. A massive solar flare -- an occurrence happening every 150 years on average throughout the earth’s history -- could also have the same impact on our fragile electrical circuitries.
Imagine life with no cell phones, municipal power, water or sewer. No vehicles would run that depend on an on-board computer. Within days, millions would be without food or water. The “math” at this point isn’t kind. Some estimates have the death rate in large urban areas as high as 90% within one year under such a scenario.
The good news is that the U.S. electrical grid could be hardened against such damage for much less than the costs of ignoring the problem. Most of the nation’s elaborate infrastructures are completely reliant on electrical power. Without it, we are in a world of hurt.