At one point it was common in most English-speaking countries as a result of some very charismatic snake oil salesmen around the turn of the 20th century.
It was a "cure-all" promoted largely by Harvey Kellogg (a proper nutcase who despised sex, loved enemas, and invented corn flakes) and a Dr. Sayre, who circumcised a few people and made a pretty big logical leap that the dick-cutting was what cured their ailments. So he went around North America and Europe and so on, preaching the benefits.. it really only caught on in the US, UK, Canada, and Australia.
In each country, things developed a little differently. In the UK, I think it was around 1960 when they decided "you know what, this is kinda stupid" and discontinued it through their health service, and it hasn't really been a thing since. In Canada and Australia it hung on a little longer, into the 70s and 80s when it largely dropped off and now a small minority of boys are cut there. But in the US...
Not only did the circumcision craze come at a time when medical science was finding out about pathogens, but it was also when proper hospitals were starting to appear. Circumcision became a status symbol: if you were rich enough to have your baby born in a hospital, you'd get him cut to show it off. Even today, especially in the South, being uncut is associated with being a poor minority (black or hispanic). Aaaand of course Americans are very, very slow and stubborn to change their views in the face of contradictory evidence, so... it's still here. Most boys are cut just for the reason of "well I was cut and I want him to look like me" or because of a vague, uninformed idea that it's "cleaner" somehow. Profiteering is probably another big reason it's stuck around in our ridiculous for-profit medical system. Might be some racism thrown in for good measure for the reason I already mentioned. In fact, I think there are stats that show that when America's public healthcare stopped covering infant circ, the circ rate among poor minorities dropped precipitously, but the rate among middle- and upper-class whites has remained almost the same. So while the stats are *better* today, it's mostly as a result of fewer lower-class people doing it.