Ignore the kids, look at the adults. They're not morbidly obese, but they are carrying excess fat. Without a change in diet, or adopting the training regime of a competitive athlete (do you know how many calories you need to burn every day to stay lean on that kind of diet?), this is likely to trend to obesity as they age.
These people are NOT obese. They are not super lean either, but for their age this looks like a perfectly healthy weight. In fact they are relatively lean compared to the other families.
Look at photographs of people 60, 80, 100 years ago. The relative perception of obesity in the US is extremely distorted. The average male is 5 feet 9 inches (176cm) and 195 pounds (88 kilograms). That is overweight. The adults in the photo are also overweight.
I'm not from the US, and neither are the people we're talking about. These people look like they weigh less than 88 kilograms, which I agree would be obese for 176cm.
Which is why it's no surprise that the Mexican family is also overweight.
But actually look at the photos of the American and Italian families. The Italians have almost half the food the Germans have, a small fraction of sugar drinks, and very little dairy. They also have one more child in the family. Which is why they look fit.
Second, how can you judge this without knowing how much calories they burn?