Compared to continental Europe, why are food portions in America so large?

For breakfast, a Frenchman can easily do with three mildly toasted breads or a croissant. An American would need cereals, oatmeals, pancakes, scrambled eggs, maybe some hot chocolate or juice. Ans, why is the main American meal full of meats. It's really unhealthy to eat more than 75 g beef or pork in a single session. Personally for me, I can't devour that entire chicken or a large fillet steak in one meal.