Look at what other OECD states spend per capita. Compare to how much the US spends per capita. For a real WTF look at how much public money the US already spends per capita. This is all a google away. The safe bet based on available data would be that moving our system to be more similar to any of those used by other OECD states would significantly reduce our spending while having little effect on health outcomes.
It's possible some other reforms that differ radically from those systems would improve things, and maybe even be better than anything other OECD states do, but since we have a wealth of real-world data about how the existing systems work and only speculation about most others, it's a much safer move to base reforms on the ones that are observably better than ours in the real world.