Many people argue so. See, for instance, this.
But the simple fact is that the US's lower life expectancy can be traced to several factors that have little or nothing to do with the quality of our health care, or access to it.
To be blunt, as compared to countries with socialized medicine, folks in the US:
1) Do more drugs;
2) Drive more miles in cars (leading to a higher accident death rate per 100,000 of population);
3) Eat more processed foods and fast foods;
4) Murder each other at a much higher rate (more than three times the rate in France)
5) and are far, far fatter.
Adjust for these causes of death, and life expectancy in the US rivals or exceeds that in most countries with socialized medicine.