If the government followed the constituion this wouldn't be problems:
1. Marijuana would never have been illegal at the federal level because an amendment wasn't passed.
2. Healthcare and any other federal welfare policies could be ennacted by passing an amendment.
If there isn't broad consensus across the country to pass an amendment then states can do it independently. There is no reason a state can't have single payer healthcare, except that they don't want to pay for it and want to just add the cost to the national debt.
You are ignoring the constitutional article granting congress the ability to make laws. Congress passed laws making weed illegal and hasn’t passed a law granting (or prohibiting) universal healthcare.
States can, indeed do it independently. There’s at least 3 states with a public option
Yeah, exactly - what can't be enacted under the commerce clause. Everything impacts commerce, growing wheat on your own land for your own use impacts commerce. It's not legitimate. Once that door was opened, it went from enumerated power to anything not prohibited.
If there isn't broad consensus across the country to pass an amendment then states can do it independently. There is no reason a state can't have single payer healthcare, except that they don't want to pay for it and want to just add the cost to the national debt.