I finally found the information I was looking for in regards to how this practice spread to the U.S.

"Circumcision gained in importance in the USA only after allopathic medical doctors, playing upon prevailing sexual anxieties, urged it as a "cure" for a long list of childhood diseases and "disorders, "to include polio, tuberculosis, bedwetting, and a new syndrome which appeared widely in the medical literature known as "masturbatory insanity." Circumcision was then advocated along with a host of exceedingly harsh, pain-inducing devices and practices designed to thwart any vestige of genital pleasure in children (Paige 1978)."

So although it probably started long before 2300 B.C., as a shamanistic ritual, the reasons for doing it have changed throughout time. It seems that it originated as a sacrifice.

It was also interesting to read that it was not always practiced by Jews. Apparently Moses outlawed the practice at one point in time.