Massachusetts did this in the program that Obamacare was modeled after, so clearly that's not (currently) illegal at the state level.

The fee structure is different (just a missed deduction on the state taxes, not a separate monthly charge), but it still works.

I'm not saying it can't be done; I'm saying its a pain in the ass due to the political climate in the US. Apologies that wasn't clear.

States have granted themselves their own taxing authority, and have autonomy in doing so.

You wouldn't just copy and paste "IRS" into the state law that a state might decide to create. You would use the state's taxing authority.

Yes, state sanctions don't generally sting as much.

But each state would have to independently decide, with its own constituents, if it could economically offer subsidized health care for all of its residents.

Many states already have some form of parallel subsidized/free health care system for certain segments of the population. Like their school teachers and their children as an example.

Anyway, hope that helps.

Some states don't tax income, like my state of Florida. They don't much care about universal healthcare, because most of their residents are already on a sort of universal healthcare if you're the right age: Medicare. I'm unsure if there's a political will to enact taxes in this state to pay for healthcare when there's only a sales tax in existence (for citizens).

States have autonomy in creating any kind of sanction they want, as long as it is constitutional, but more practically as long as no judge finds that it is unconstitutional.