I think this is right. If not a deliberate poison pill, implementation of the ACA was a strong "foot in the door" technique for those who want single payer. Though, even before the ACA, the government is deeply involved in the system (employer based tax incentives, Medicare, etc)

I don't find that surprising though. I think Obama himself said that ACA was just a start and would have to be revisited. (Citation needed, I know.) What's amazing is just how bad conservatives have been at articulating the free market case for health care and insurance.