(1) Is PTSD prevalent in other cultures/countries? Is it a major issue primarily in industrialized countries, or is it present in all cultures engaged in conflict? Russia has a serious problem managing PTSD among combat veterans returning from Chechnya, but this would seem to indicate that PTSD is a consequence of industrialized war.
Answer part one: yes

Answer supposition part two: no

Case Studies: Rwanda -- hardly industrial

Congo -- Ditto

There are plenty of others.

Do cultural mores help define what constitutes trauma? Probably in that what is terribly horrific in one place could be a minor hiccup in another.