>Drinking age is tied to necessary federal highway funding, so states aren't going to lower the age.

Federal mandates for funds exist because the 17th amendment took away State governments representation and handed to popular human vote. Few Senators faithfully representing their State would pass mandates telling their own government they must comply or not get money. They'd likely get removed or replaced with someone else by the state government that put them there.

> Universal healthcare requires high buy-in and very different systems from what we have now.

States can regulate all of them. They are under no requirement to follow federal policy. In fact, they can even erect pretty substantial border controls (like California does) and send armies to protect their borders, if they really want to (yes this has actually been done outside the civil war).

For example, California recently 'threatened' to start universal health care. I'm unsure why the news framed it this way given that it has always been california's right to provide free health care to its citizens, and no one can really legally stop it. Perhaps California cannot raise enough money to do so, but that is an issue of feasibility, not legality. It's not like the feds would magically be able to raise money that California couldn't.

> Drinking age is tied to necessary federal highway funding, so states aren't going to lower the age.

Um sure, but states are not required to take federal funding for highways. That's like saying 'Aunt Irma requires me to send her a Thank You note whenever I ask for her knit sweaters', while neglecting to mention that you actually do want the knit sweaters because they keep you warm and cozy.