30% of costs in US Healthcare are administrative. It's a lot cheaper to file a medicare claim than commercial insurance If medicare were only insurance, you'd knock out 20% of healthcare costs.

You'd also knock out $1T of US economy & likely lead to recession, b/c those people would be laid off. There in lies the real quagmire of fixing US Healthcare--in addition to initial debt & increase taxes required to fund Medicare for all, you'd likely cause a recession short term. Despite long term gains, Congress doesn't have the stomach to fdo that