I'm sure there are some cultural differences, but keep in mind 30-40 years ago we didn't have huge quantities they way we do now, and we didn't go out to eat the way we do now. It took time for the cultural norm to catch up to our ability to overeat.
While other countries can now afford to overeat as easily as we can, they've been able to do so for a lot less time. Again the charts for percentage of the population that is overweight and obese back up this hypothesis--other developed countries are trailing behind the US by about 30 years. They have just had less time to make a habit out of over-consumption.
Also, most other developed countries still haven't caught up to the US in terms of affordable overeating. In PPP terms the US ranks 10 in GDP per capita, higher than every other major economy and higher than almost all of Europe by a very significant margin.
While other countries can now afford to overeat as easily as we can, they've been able to do so for a lot less time. Again the charts for percentage of the population that is overweight and obese back up this hypothesis--other developed countries are trailing behind the US by about 30 years. They have just had less time to make a habit out of over-consumption.
Also, most other developed countries still haven't caught up to the US in terms of affordable overeating. In PPP terms the US ranks 10 in GDP per capita, higher than every other major economy and higher than almost all of Europe by a very significant margin.