> who makes it happen and enforces the rules?

Congress for the first. Either the FCC or, my preference, private litigants for the second. (Treble damages for stupid suits, though.)

> For all content or just “political”?

The courts can already distinguish political speech from non-political speech. But I don’t trust a regulator to.

I’d borrow from the French. All content within N weeks of an in the jurisdiction. (I was going to also say any content that mentions an elected by name, but then we’ll just get meme names and nobody needs that.)

Bonus: electeds get constituent pressure to consolidate elections.

Alternative: these platforms already track trending topics. So an easy fix is to slow down trending topics. It doesn’t even need to be by that much, what we want is for people to stop and think and have a chance to reflect on what they do, maybe take a step away from their device while at it.