On balance, I would say in spite of the nanny state. The greatest and most impactful advances in medical knowledge over this time frame came mostly from the private and voluntary sectors in the United States, rather than government. Certainly Obamacare in and of itself, by rationing and restricting access to medical services and by impeding medical research by decreasing profit incentives, will not have a positive impact on life expectancy in the United States.
I don’t believe life expectancy has changed all that much.
I’ve tracked my ancestry back to the mid 1600s and find a lot of people living well into their 80s. Men tended to live longer but I attribute that to the fact that they weren’t pregnant 15 or 16 times. Lots of children died but if you were a male who survived to adulthood, chances are that you would live as long as anyone today.