Simply put: Our food is more processed here. Our country allows ingredients that many European countries do not. They don't use fake sugars like aspartame, high-fructose corn syrup, processed chemicals, artificial flavors, and dyes. They don't allow genetically modified foods in their country while we are now just labeling them.
The French approach eating differently too. They eat smaller portions and stop when they're full. They're always eating fresh, colorful, fruits and veggies, and butcher-cut meats including nutritious organ meats, which we scoff at.
Their largest meal is during the day at lunch whereas the majority of Americans' is dinner. They're burning their food off during the day while we're going to sleep right after our biggest meal.
They also don't snack like we do here and don't indulge in "junk food." The French eat only when they're hungry, and they actually take the time to enjoy their meals—usually with a glass of wine.
We can learn from them by snacking less, eating our largest meal during the day, and sitting down to really enjoy our food.