It "literally" did not. What enforcement exists is financial (a tax penalty) and not compulsory. And obviously most people are covered via employer plans or Medicare, as has always been the case. A quick Google says that 19.2M Americans are enrolled in ACA plans. I don't have statistics, but I'd bet that the overwhelming majority of those are willing purchasers. Most people view health care as desirable.

The "everyone has access to the ER" has to be paid somehow, which is through tax dollars. The USA has a for-profit health system but typical neo-liberalism has a safety net where corporates get to dip into a different bottom-less pot. So it makes sense that we make this visible by taxing everybody who isn't paying their own insurance, since they still expect access to ER.

No, it didn't. If you didn't want to buy health insurance, you just had to pay a couple extra thousand in federal income tax:

https://landline.media/affordable-care-act-tax-penalties-end...

>The penalty for not having an ACA-compliant plan or forgoing coverage in 2018 is the greater of $695 per adult and $347.50 per child for a maximum of $2,085 or 2.5 percent of adjusted household income. The percentage penalty is capped at an amount equal to the national average premium for a bronze plan, the minimum coverage available by law