Why does go expectancy of United States status so low?

While the United States lead the world within medical technology and medicine, why does our go expectancy rank 45 among developed nation?Why does go expectancy of United States status so low?
There are several reasons, but I will bestow you two. One is the obesity horizontal in this country-tech and prescription can only fix the consequences of tubbiness to a point. The other is that we save babies that are born at a much younger gestation than most countries. The majority of these micro-preemies do not live especially long, thus bringing down the life expectancy age.
because medical insurance is so large most Americans can't afford it.