The Short Answer
Cultural PTSD theory says that on a cultural level we are thinking and behaving in many important ways like people with PTSD think and behave. That is not to say that we have all been exposed to trauma or are having our own individual experiences with PTSD. What the theory says is: many general Western cultural norms, values, and assumptions appear to be quite similar to issues people with PTSD typically struggle with. And because these are cultural level norms, values and assumptions, we are all affected by them.
If you are well versed in trauma issues, I want to note that this theory is very similar to intergenerational or trans-generational trauma in many ways. The main difference is it is about general Western norms, values and assumptions (rather than specific groups living within the larger culture).
The theory explains how power and control needs become more important in the aftermath of trauma, and how that then becomes problematic, both for individuals and in larger cultural contexts.
The most important implications of the theory are how cultural expressions of power (brought on by typical trauma based reactions writ large) have led to things like empire building, colonization, oppression of various groups, and several more issues.
The theory has six main points.
Here is an article that summarizes the theory. A full book, Cultural PTSD, The Impact of Humanity’s Trauma Filled History, is upcoming.
All of the articles beyond the condensed summary that are available on this website are draft versions of sections in the full book. Many have already been substantially revised for the book.