"Many of the important factors – smoking, obesity, violence, poverty – are not about providing better healthcare for those that need it, but about preventing poor health outcomes in the first place."

I think we should provide every US legal resident with affordable access to health care, but the lack of it doesn't significantly impact life expectancy at the aggregate population level. Only about 10% lack medical insurance. Other factors like obesity, substance abuse, lack of exercise, and preventable trauma are far bigger factors pushing down national life expectancy.