Well everything and nothing. The world moved under our feet and yet we won't feel anything right away. But some random thoughts.
No more sniffles in the Emergency Room. If you're kid is sick you take him to your doctor, or to Bernie Sander's newly funded Community Health Centers. 15 million people, including for the first time working poor singles, will be added to Medicaid, if you need to see a doctor you make an appointment, or walk in.
Near elimination of cost shifting due to non-reimbursed care. Currently hospitals are squeezed from both ends, on the one side having to negotiate with insurers to lower costs, on the other side providing care that they know they will never be able to collect for, and in the middle the uninsured or underinsured who get the resultant cost-shifting, and if they have assets can end up losing them all. Over time this should just level out, a medical procedure will cost what it does, whether you are publicly or privately insured. And among other things this will revolutionize charitable hospitals including the Catholic and Jewish systems. In my town both main hospitals are run by the Sisters of Providence who have a sterling record of writing off care to those who can't afford to pay, in turn sucking down huge amounts of money from the various parishes that support them, now those donated funds can go other directions.
No more collection jars on the store counter for poor Lexi or some other child who can't afford a needed operation. No more TV features of some struggling family facing destitution because Dad maxed out his lifetime limit on his insurance and Mom is still sick, no more stories about how in the richest country on earth people could still be dying because they simply couldn't afford the care anymore.
Things you would never have thought of. Nowadays people have medical riders on their car insurance in case of traumatic injury. Probably no longer necessary except perhaps for long term care. Same with AFLAC and other suppliers of supplemental insurance, with no annual or lifetime limits why carry a cancer policy?
Transformation of the labor/employer power balance. Practically every major labor struggle over the last twenty years has revolved around health care coverage with employers implicitly or explicitly threatening to just drop it altogether if they don't get the wage or cost-sharing concessions they want. Now in a lot of cases they won't be able to drop coverage even if they want to or have to pay a per employee subsidy to the Exchange to help pay for individual coverage.
These are just random thoughts on the morning after. But we haven't begun to think through all the ramifications of this.