from Paul Craig Roberts at paulcraigroberts.org:
In his newly published book, Nuclear High-Attitude Electromagnetic Pulse, Steven Starr shows that all it takes is one nuclear explosion to shut down the United States and throw the population back into the Dark Ages. The electric power grid would be destroyed along with the communications system, the cooling systems at nuclear power plants and all electronic devices. The reason is that civilian infrastructure is not protected from ElectroMagneticPulse (EMP). The military has taken steps to shield its weapon and communication systems, but nothing has been done to protect civilian infrastructure. Bills mandating EMP protection have been defeated in Congress.
Starr reports that only 4% of the US military budget is required to shield the power grid and civilian infrastructure. Instead, the Washington idiots waste trillions of dollars in pointless wars in Afghanistan, Iraq, Libya, Serbia, Syria, Yemen, Palestine, and Ukraine.
American cities would suffer no effects from blast and fire, such as would be produced by ground level detonation, but the consequences would be just as dire. Starr describes them in a summary on his website: https://nuclearfamine.org/connect/