If an idea isn't triggering action, does it really matter how popular it is?

True.

The problem in the US is that a large chunk of the population have been trained to be anti-tax regardless of goal.

They'll support Universal Medicine hypothetically but as soon as you talk about the required payroll tax they'll oppose it, even if it is lower than they're paying now in premiums. Then the conversation will immediately turn into a "government cannot be trusted"/"stealing my money" etc.

People will love it once it is online, just like the ACA/Medicare/Social Security, but getting it online is politically radioactive and will sink both the politician and party until people realize they love it.

"Universal health care" is actually a broad term. The problem is that people agree on the broad principle, but disagree on the details and can;t come to a compromise. Thus, nothing gets done.

Not for lack of trying. It's only ONE person who is blocking action, which is Mitch McConnell refusing to even consider bills in the senate.

It is still in the power of the people to replace him as majority leader of the Senate, if they want to unblock that logjam.

He's elected by his peers in the Senate. They're all responsible for blocking action.

Yes. It means that you can make the action happen if you can fix the broken reward model.

(What is the political equivalent of dopamine signalling?)