"... where on earth does Mr Forstchen get the idea that the USA would be taken back 300-400 years considering electricity generation hasn't been in widespread use since the the early 1900s ..."

I suspect he's closer to being right than wrong.

For the first 300 of those 400 years, people knew how to survive where they were, with simple implements. In every settlement, most of the people knew how to grow food, one or two knew how to work metal, one or two could make wagons and wheels, some could make fabric, most could make clothing from scratch, someone could make boots and shoes, a few guys could build a grist mill.

The U.S. has 300 million people -- how many of them could do ONE of those things? Not very many.

It isn't the lack of electricity itself that we are so dependent on, it's all the things we need and use that are, in some form, based on electrical power.

America mostly manufactures for heavy industry. We've outsourced much of the 'simpler' stuff. Slam the import doors right this very minute, and we're going to be in a world of hurt. How are we going to suddenly crank up production just for things we need to survive, and do it without electricity?

Imagine molds carved by hand, basic materials collected and processed by hand, put together and built by hand... for 300 million people.

Food alone would be a massive problem, with overwhelming starvation. Who really knows how to grow it? Who even has seeds right in their home? Has their soil been improved, or is it solid clay or nutrient-poor sand? How many people have gardening books on hand, so they even know how to grow it? And if they can grow it, how do they preserve it for the other three-quarters of the year? Can it? Do you have the glass jars and lids? How many people know how to make containers from glass? There probably wouldn't be any lids, so they would have to use paraffin. Where do they get the paraffin? No jar lids means no pressure canning, just hot-water bath canning, and probably some sugar. Drying in humid country requires heat and insect protection. Pickling requires salt or vinegar. Does everyone have a goodly supply of salt and sugar and screening or netting?

How about medicine? Talk about the Dark Ages! No autoclaves, no centrifuges, no electron microscopes, most diagnostic equipment are just doorstops, no incubators, and most of the medications will probably be herbal (that strange old lady down the street with the 17 cats and her three acres devoted to herbs, everyone's new best friend!). Can you imagine how today's doctors would be dealing with the problems?

How fast can you manually shear a sheep? Pick enough cotton to make a yard of fabric? Pit a bucket of cherries? Shell a bucket of peas?

And I see two more problems: mostly the older people are likely to know how to 'do' things, but most aren't likely to have the strength and stamina.

The younger ones with the strength and stamina, forced to do actual menial labor? Stoop labor? Planting and harvesting potatoes by hand? Digging and preparing soil? Weeding by hand?

The MeFirst and Gimmee Generations doing this kind of labor? The tantrums, the screaming and the foot stamping would be heard from California to Maine, from Washington State to Florida!

Actually, I think the author understated his prediction. I think we would be taken right back to the Stone Age.