I'm surprised no one has mentioned diversion of federal funding from other areas. Lowered military spending, for example, to free up a significant amount of money for health.
That's not to say that cutting military expenses is the end-all, be-all but I think the most important changes to make are:
1) decreased military spending
2) addressing social determinants of health, i.e. empowering hospitals and clinics to address those factors of primary care that lie outside of the doctor's office (i.e. medical institutions partnering with food banks, legal agencies, housing departments, transit authorities, etc.),
3) reorienting the clinical experience, i.e. less dependence on expensive tests like constant MRIs and CTs and more focus on listening to the patients social factors that give primary insight for diagnosis.
I realize that each of these points is interwoven with so many other things. For example, for point 3, sure it would be great to make physicians less reliant on expensive technology and train them to read between the lines but now we are delving into the whole medical education system and reforming how med students are taught. Just curious as to what others take on this may be.