I came across a 2019 research article when I was working on the CPTSD bibliography about the percentage of people in the USA with Complex PTSD and its an absolutely staggering number:
An estimated 3.8% which for the US population of 331,002,651 = 12,471,600
We all knew the numbers were high but it's still jaw dropping when you see an actual figure.
Reference: "ICD-11 PTSD and Complex PTSD in the United States: A population-based study" https://doi.org/10.1002/jts.22454.