the anomaly of an American Army CWO staying in an RAF Officers' Mess
Not
necessarily an anomaly
Haraka.
In some respects their top rank (CWO-5?) is regarded as Wg Cdr equivalent. I think in RAF terms it's more like Spec Aircrew (but not PA!) but with more ranks.
Certainly a lot of the instructors at Rucker are CWOs, up to and including those positions which would certainly be sqn ldr or wg cdr on RAF Stations.