Everything that user "Sirap" says...plus milk and sugar. You will find milk added to so many products in the US. Why? Because the dairy lobby is powerful. Corn syrup is defintely added (as Sirap noted) but so is sugar. Bread, particularly buns, in the US often taste like light pastries in Europe because the US adds friggin' sugar to so many foods.

Let's make a little guestimating: Add +/- 50 extra calories in fats and sugars per day to US intake. US residents have +/- 50 fewer calories burned per day by their extremely limited walking. 100 calories net difference to our example Frenchman. Mon Dieu! That is 700 calories per week! A pound of fat takes 3500 calories to burn. So our average Yank compared to a similar Froggie is going to put on 3/4 of a pound per month, or about 10 pounds per year.

Now we're just guestimating here and doing averages, and the math above obviously doesn't hold up over decades (i.e. using that calculation the "average" American would put on 200 pounds over 20 years). That being said, my experience traveling back and forth between Europe and the US for the last 30 years, plus a lot of clinical data says that 50 pounds over 20 years is well within the averages, actually under the average as 42% of all US adults 20 and over are obese, which is ~35 lbs or more overweight.