The reason general anesthesia isn't used is because it's too dangerous rather than because it's not necessary. In Scotland, the NHS won't perform circumcisions before the age of six months specifically so that the child is old enough for GA to be used. It's possible to perform adult circumcisions with local rather than general anesthetic too, but since it's harder to strap them down, and they actually have a say in the matter, GA is almost always used.
Even if I knew that I or my son or any future sons would need to be circumcised at some point in their life, I would leave it till as late as possible. The risks are less, GA can be used, and the person whose body it is can get to choose what kind of circumcision they want. The RACP has said that "One reasonable option is for routine circumcision to be delayed until males are old enough to make an informed choice." There are plenty of countries which circumcise, but don't do it till the boys are over ten years old btw.
With a neonate:
a) you have to separate the foreskin from the glans (probably the most painful part of the procedure). This also results in adhesions, skin tags and skin bridges. If you wait a few years, then the foreskin separates naturally.
b) the penis is much smaller so there's more chance of a seriously botched job. It's very rare, but some babies die or suffer amputations because of circumcision. David Reimer is the most famous example, but there are several others. The record payout for a botched circumcision is $22.8 million. It was said at the time that the victim "will never be able to function sexually as a normal male and will require extensive reconstructive surgery and psychological counseling as well as lifelong urological care and treatment by infectious disease specialists." In April last year, a jury in Atlanta awarded $1.8 million to a boy whose penis was severed in a botched circumcision five years earlier. Another child lost part of his glans within the last 12 months. Sure, cases like that are very rare, but why should they happen at all?
c) there's more chance of a slightly botched job too. If you look up the
galleries of botched jobs, one thing that may surprise you is just how many jobs were botched cosmetically, rather than medically. Skin bridges, penile varicose veins, and hair growing half way up the shaft are not normal, but would not be counted as medical complications.
d) you can't use GA, so it's more painful. Medical students were still being taught until the 80's that newborns didn't feel pain, despite the obvious evidence to the contrary. A couple of recent studies suggest that neonates may actually be hyper-sensitive to pain. Just because babies don't remember, it doesn't mean it hasn't affected them. They have more problems breastfeeding, and also show more reaction to injections years later.
The problems with breastfeeding are mentioned in an AAP policy statement:
"Available research indicates that newborn circumcisions are a significant source of pain during the procedure and are associated with irritability and feeding disturbances during the days afterward."
e) newborns don't have much of an immune system, so they can die of things that are harmless to adults or older children. A baby died after circumcision in New York a few years ago after contracting HPV from the mohel for instance, and another got brain damage.
f) neonatal circumcision is strongly linked with meatal stenosis.
g) neonatal circumcision often needs a second operation. The revision rate seems to be around 5%, though figures from 1% to 9.5% have been reported.
h) a newborn can't tell you if he actually wants to have the most sensitive part of his penis removed or not. It's HIS body after all.
The Canadian Paediatric Society, Royal Australasian College of Physicians, British Medical Association, and Royal Dutch Medical Association all disagree with you in their official position statements on male circumcision. Around 50% of male doctors in Canada and the UK will be circumcised, and over 80% of male doctors in Australia and New Zealand. Why would circumcised male doctors be against circumcision? Why is it so easy to find doctors who were circumcised as infants, but are opposed to infant circumcision, but almost impossible to find doctors who weren't circumcised as infants, but are in favor of infant circumcision?
That last paragraph is by far the most important. If you respond to any of this, please explain why those four medical organizations have such a different view of circumcision.