With today’s nuclear weapons an enemy need not ever set foot on US soil to defeat it.
Two or 3 EMP weapons exploded over the US would result in total electrical power loss to the nation, causing the deaths & starvation of the majority of the population. Most of those that survive will be living a 19th century lifestyle for years to come - candles for light, fireplaces & campfires for warmth & cooking, boiled water to drink.
Without power commerce would slow to a trickle, there would be few open stores, no goods on the shelves, no food at the closed grocery stores, no gas at the pump even if you could get your car to run. Transportation & communications would stop. Banks are closed, credit cards don’t work, checks are worthless, & the dollar may not buy much. Government, if it can function at all, would be powerless to do more that invoke an unenforceable martial law.
Probably 75% of the people would die within 6 months. They will continue to die without proper nutrition, health care, & shelter from the weather.
At that point, an intact South African army/navy could conquer our land if they so desired. The continental US, largely uninhabited, would be an excellent place to colonize!
“Two or 3 EMP weapons exploded over the US would result in total electrical power loss to the nation, “
Nope. The Soviets tried it over their land and it only blew one transformer.