You don't need a nuclear war for all that to happen.

As I once read in one defence publication, USA is only 4 biggest fertiliser complexes away from the famine, assuming the assailing party can blockade the country to prevent food importation.

The same is for the biggest oil, and fuel manufacturing complexes.

USA is also "just" 50 power stations away from the grid becoming useless. USA is though much, much better off than most countries on this, as its power generation is much more decentralised, thanks to largely private operation.

USA has domestic capacity to manufacture small, and medium sized turbines, but largest ones used in the superplants mentioned above are made by GE Energy in France, and some even in Japan, and China.

The same for big, top tier transformers for the grid.