I'd never heard anything about this, very interesting. You hear about "Buffalo soldiers", the 54th Mass, Irish brigade, etc. but never about other minorities. I found this that might be of interest, albeit dubious accuracy as the article says the 1st Penn Vol Cav were called Cameron's Dragoons, instead of the 5th, but according to Penn state records, the Camerons
were designated 5th, although there's no mention of the regiment being Jewish.
http://www.jewish-history.com/civilwar/mmallen.htm