> ....which would explain why every first world country uses it except the US?
Every first world country except the US has something approximating universal coverage, but not all of them use single-payer (or even a single basic coverage insurer with supplemental coverage from other payers.) Compulsory-purchase insurance models similar to those in the ACA (but, you know, actually universal) with private insurers are not unheard of (e.g., Switzerland uses that model)
Switzerland's is interesting in that it goes a step further than Obamacare and really makes it compulsory, rather than simply fining you for not having insurance. A colleague was a postdoc there for a while and didn't understand the system, and after ignoring a few letters telling him he needed to buy insurance, he got a follow-up letter telling him that, as he had not yet enrolled in a plan, a default one had been chosen and he was now enrolled in it.
Every first world country except the US has something approximating universal coverage, but not all of them use single-payer (or even a single basic coverage insurer with supplemental coverage from other payers.) Compulsory-purchase insurance models similar to those in the ACA (but, you know, actually universal) with private insurers are not unheard of (e.g., Switzerland uses that model)