I'm sure there are 100's of factors, but the most basic seems to be portion control issues. People's idea of normal portions in the states (in general) is different from other places. The #1 complaints from American customers here is that portion sizes are tiny for the price (and this is just Canada which has larger portions than say, Europe). I think the portions are huge, but yes, compared to American portions they are still small.
Here in Quebec, people eat high fat/high carb foods/lots of alcohol. However, having a tiny piece of high fat brie, some raclette (melted cheese on meat slices) and a few slices of white bread is considered enough of a meal at a party. Food is not the centre of the event, the wine and talking is. In the US, I found that food was the centre of the event, and the booze/talking was a side-note.
Food and grocery is quite cheap in the US, compared to here. We used to drive across the border every weekend to shop for groceries because of the vast difference (even rural Sumas, Washington state was cheaper than urban Vancouver, Canada, despite most things being trucked 2 hours from Seattle). In France, you'd be shocked to find a soup with piece of bread for 6-8 Euros (around $8-10 US) which sounds outrageous compared to American prices.
Just an observation from an outsider
