The only problem (compared to other countries) with US healthcare is its outrageous cost. There is zero evidence that healthcare quality is to blame for the slightly lower life expectancy.
I only have a few anecdotal stories to go by, but I know at least one with back problems and one with heart problems stuck where they got on-and-off health problems that lead to problems paying insurance that lead to the being effectively outside the system and any insurance that will take them on now excludes everything related to the their pre-existing condition. All they get is emergency care, when they should have had surgery. So I definitively think distribution of care is still some part of the lower life expectancy, those with lots of money get overtreated leading to good quality at excessive cost but those with no money get undertreated too.