If you are an American male who was born between the 1970s and the 2000s, you were probably circumcised regardless of your religion/ethnicity.
The explanation for why circumcision is more common in the US than in Europe among non-Jews/Muslims is that because we have a for-profit, private healthcare system that relies heavily on fee-for-service payment, doctors have an incentive to encourage parents to have their babies circumcised because that's an additional procedure that can be billed for and is very quick and easy and low-risk to do.
Medicaid, OTOH, has crappy reimbursement rates and may either consider it an elective procedure or just pay so poorly for it that doctors don't want to be bothered.
Your reasoning is right, but not so much for data. The years of near-universal neonatal circumcision (roughly 85%) ran from roughly post-WWII to the 1970s. Certain trends have stayed persistent. Ethnicity actually is a significant variable, as is region (it's most uncommon in the West and most prevalent in the Midwest). Circumcision is very rare among Hispanics and slightly less rare among Asians. If you look at a state like California, where the overall circumcision rate has been in the low 20s over at least the past 20 years, it's been less than 10% among Hispanics and less than 40% among whites. See this map for overall neonatal circumcision rates within the past few years:
As for health insurance, I agree entirely with the above. There is literally no other country in the world that advocates for infant circumcision outside of a religious context. As for Medicaid, it covers between at least 40-50% of births in this country. When circumcision moves from included in health benefits to not-covered, it becomes a lot less prevalent. California's Medi-Cal was the first state to stop covering the procedure in 1982. It's isn't a 100% correlation, but see this map for Medicaid ceasing coverage versus total neonatal circumcision rate:
Poll
