mid-1800's in England...would he use his "Bell Curve" theory to support the notion that the genetics of the Irish people were the reason they were so uneducated and unable to solve their "Famine Problem"...I really don't mean to be 'snarky' toward you...at all...but my cultural history and your reference to the Northern Irish situation caused an almost "knee jerk" reaction...
That being said, I have grave misgivings about Charles Murray as a person, and more importantly, his philosophy...(see following links)...
https://www.splcenter.org/fighting-hate/extremist-files/individual/charles-murray
https://en.wikipedia.org/wiki/Charles_Murray_(political_scientist)
To me, he's just another "Eugenics" promoter...and that's a "show stopper". the "Bell Curve" analogy is simple observable fact...for any group of people...or the whole human race...but to slap a genetic racial label on it is not factual or logical.
Now, to the issue of "Systemic Racism", I offer the following link of an interview of Coleman Hughes by an Australian, John Anderson...
https://www.youtube.com/watch?v=gxLJCXKT8MQ&t=180s
You need only go to the 5:50 mark and stop at 9:00...or watch the whole thing...Mr. Anderson brings up the notion of "Racism of the Heart", to which Mr. Hughes acknowledges...saying (my recollection, but verifiable in the video)..."Legalized Racism" ended in 1967, however, the more difficult challenge..."Racism of the Heart"...has yet to be resolved.
This is what I believe is today's problem...there is a significant residue in the USA of "Racism of the Heart" which all of us need to acknowledge and speak out agains...It seemed to me that you "get this" in your commentary, but I'm very much interested in your take.
Note: Both edits for spelling (my bad).