Cycling is one of few sports where poor diet is a benefit. The euro rider eats moldy cheese, fish caught out of polluted waters, pasta and bread. And they eat stuff like hearts and kidneys, gizzards, and lamb tripe. The average euro rider is much smaller in stature compared to his american counterpart.
The average American is feasting on corn fed beef. Packing on the pounds at an early age. Growing beyond normal size. Those early years of soda, hormone enriched milk, and sugar, lots of sugar, are a detriment. 6 foot 4 inches, 250 pounds, size 15 feet, football or basketball are the sports of real men.
Then you have your British riders. Tea and scone types. How Tommy Godwin could ride 75,000 miles in a year on tea and crackers is a wonder.