Circumcision became common across the English-speaking world in the late 19th century as a quack cure for masturbation and venereal disease. Particularly masturbation, which Victorians thought caused a wide range of ailments, especially retardation. Historically, circumcision had always largely been limited to Jews and Muslims. The growth in popularity across the Anglophone countries is something of historical anomaly; it didn't spread to any other European countries.

When the UK introduced the NHS in the 1940s it was determined that since there was no obvious medical benefit to circumcision it wouldn't be offered as a free procedure. After that, circumcision declined rapidly. Australia and Canada don't have the same level of centralisation in their healthcare systems, and it took until the 1970s for doctors to start recommending against it, so a decent proportion of Australian and Canadian men are circumcised (mostly older men). Circumcision is declining in the US at this point, so it's really only a generation behind Australia and Canada; if the US's healthcare system played a part in the fact that circumcision survived for longer, it's more because there's no central authority that can de facto ban the practice.

Follow up question, could a correlation be made between the popularity of circumcision in the US, and the pay per service health care system that's widely used here? Meaning, could it's popularity be linked to the fact that physicians can bill the health insurance companies for performing the operation?