Is circumcision of a 3 year old baby traumatic or harmful?

Traumatic,can U wait. Psychologically age window beween 3 - 5-years is developmental not a good interval in time for boys to undergo genital surgery.Toddlers instinctively know that their penis is very important, but can not process the need for such a procedure.Hopefully this is not an urgent & u can wait couple of years.Consider steroid cream to loosen freskin and reevaluate in a couple of years so he can rationalize.
More trouble than NB. Circumcision for a 3yo is more problematic than for the newborn. Differences in blood flow & size require a different technique & the kid will need a general anesthesia. After the procedure there is more post operative swelling, bruising& general discomfort. If not needed for a specific medical issue i would put it off until the kid was a young adult & expressed a desire for the procedure.
A Bit of Risk. At this age, the procedure is performed under general anesthesia.There may be complications of the anesthetic or surgery.But other than minor discomfort, the child usually does fine. In my opinion, at this age, circumcision should be done only if the uncircumcixed child has serious problems, such as frequent infections.