THIS.
smegma smells bad yes, but just because something smells bad doesn't suddenly mean it is evil and disease ridden, it is as Eveiebaby says ANTI-BACTERIAL so all people using the hygiene argument fail and clearly only listen what what idiots tell them without actually backing up any of their information with evidence.
medical circumcision is one thing, religious is another and the rates of circumcision in America are quite another still.
Valid medical reasons are rare, phimosis and paraphimosis are very rare along with the bacteria (and occasional birth defect) which are linked to causing them. Even then, circumcision is the final option too be used in the most serious cases as manual stretching and steroid creams are the main cure. immediately circumcising someone with phimosis is like immediately removing the an ingrown nail....
I find that the religious reasons make no sense in my understanding of religion. If god made us all in his image (asuming god is perfect as religions say) then god has foreskin and yet he tells 'us' to remove it as it is impure/nasty/etc. Therefore god is also not perfect, why would he ask his creations to remove a piece of anatomy that was originally his design which he claims is perfect?!
Circumcision in American culture is for a different reason (ignoring religion). At first it became popular through the medical institution believing it had (magical) curative effects for all sorts of diseases and illnesses, this was in the time when 'germs' had just been discovered and there was a huge media storm driving less educated people into a frenzy. The logic of: it smells bad;therefore it must cause disease was used. Thus it became entrenched into the system. fathers wanted their sons to be like them and not be different from the other boys.....Not to mention the doctors who performed the simple 10min operation at birth were paid to do it by the families, and such they sold it on bogus health benefits to gain easy money.
Countries with national health services avoided such underhanded greedy doctors by not paying on commission in such a way and running extensive surveys into the matter to decide if it was a viable medical procedure or an operation as outdated then as lobotomies are today, the results are obvious...