I think you are misunderstanding most, if not all, of what I wrote.

I never claimed that we weren't unhealthy but that being unhealthy isn't "American culture" as evidenced by different demographics in America having markedly different obesity rates. The obesity rates are similar among similar demographic groups in different countries - e.g. white people in the US have similar obesity rates as UK, Canada, and Australia. It's very weird to say that this thing that is constant among demographic groups across countries is dependent on the culture of one country. Especially when it is different among demographic groups in the same country.

I am not implying that white people are genetically predisposed to obesity. Actually, what I wrote is the exact opposite. I suggested the obesity rates were due to environmental factors and, crucially, I pointed out that other racial groups have greater obesity rates. So, I explicitly stated I believed the difference was not genetic and that white people have less obesity in the US than non-white.

For the other points you seem to prefer using a different metric, overweight instead of obesity. You haven't said why that factor is more relevant or how it changes what I wrote above.

I am studying in Russia and one of my teachers told me that it must be so that North Americans have some disease that has made them all so large. It was after I told him two of my neighbours had tummy tucks in the same month... he did not know what that was.

I would contend that physical activity is probably not a large determinant of weight, although physical activity is an important determinant of health.

Yes and no.. on a strict thermodynamics basis, it's not. If you're say 30lbs overweight (i.e. some, but not much), straight up burning that is going to require considerable patience and discipline to not destroy your body in the process. Each lb of fat is - very roughly - equivalent to running a marathon.

However, being physically active makes you more aware and mindful of the input side of the equation; building muscle mass, cardiovascular fitness and endurance in turn improves your metabolic ability to burn calories. So it's absolutely part of the picture. "The Miracle Pill" by Peter Walker is an excellent introduction to the topic.