Earlier quoted context omitted.
I encounter a lot of people with the "species-ending nuclear winter" false belief, and their attitudes are usually something like, "Oh, what can you do? Just have a drink and enjoy the fireworks." I get the sense the author is working against this line of thinking, because there is in fact a lot you can do (both in terms of preparing and in terms of responding).
How do you prepare for the complete breakdown of society and 200 million survivors competing for resources that will support maybe 15 million people in a blasted, utterly destroyed landscape with no infrastructure or production.
Setting the Western world back a century is probably correct. The balance of power would shift to the global South.