We have the medical care/drugs to address symptoms of diseases (like diabetes, etc...) AFTER they happen. But we do a horrible job of preventative care, and it’s one of the reasons why healthcare costs are so high.
American life expectancy has actually gone down in recent years (due to numerous factors, not just poor diets) —but in general, it has actually lagged behind developed Asian and European countries.
Careful with a straight up comparison of life expectancy between Europeans and Americans. There are ethnic differences. For example, heart disease is more common among African Americans as is low birth weight. To get a more accurate comparison you need to compare like with like.....ie Danish Americans with Danes. Things look rather different when you make that comparison.
Another important thing to remember is that in European countries babies under a certain birth weight which have a high mortality rate are not defined as “live births”. In America they are so when inevitably a relatively high percentage of them die it drags down average life expectancy in America.
Then there is the matter of obesity. America is a bit ahead of most European countries on this unfortunate curve though the Europeans are catching up quickly.
Lifespan alone is a poor measure of how healthy the food is or how effective the medical system is.