If you were in his place, would you really want amputation to be among your first experiences of your new life in America?
Uneccesary trauma isn't the only reason to allow him to keep his entire body he was born with, so please consider these additional concisely-written reasons: http://www.naturalfamilyonline.com/5-bc/64-no-to-circumcision.htm
Here is a mainstream news article on involuntary genital reduction surgery and trauma. However, please note, that even if it could be done with zero pain, it is still the amputation of a healthy functional body part from a non-consenting member of our society. http://www.cnn.com/HEALTH/9712/23/circumcision.anesthetic/