You certainly have some valid points. Having recently finished a senior seminar paper on weight issues in America, many of your points are correct.
The major problem in America is a lack of activity (sedentary lifestyles). We turn to televisions and computers for entertainment. We take sports out of schools. We drive almost everywhere. Our jobs are sedentary in nature.
In America, portions are out of control. This is due in large part to the availability of nutrient poor ingredients like flours, sugars, and hydrogenated oils. Unfortunately, many Americans have to choose between eating nutrient poor foods and going hungry. Healthy foods are extremely expensive and unattainable for many low income individuals.
Surely, the government has a large role in regulating our food. Corn is extremely cheap to buy because it is nutrient poor. The government allows additives to be put in just about everything. One is hard pressed to find products that do not contain corn syrup, food starch, or other harmful ingredients.
You are also somewhat correct about diet foods. The majority of diet foods are labeled as "low-fat" or "low-calorie." That translates to high in sugar. When the fat and calories are taken out other things are added. This usually includes sugars and hydrogenated oils. Products billed as health foods are often harmful foods. I do believe that Splenda is a safe alternative to sugar. Just about everyone knows the harmful effects of regular sugar. Numerous tests have proven the safety of Splenda.
However, I think you missed the point of low-carb dieting. Low-carb dieting is about eating healthy, whole foods. Atkins is the reason that we are so aware of dangers like sugars and trans-fats. As a successful low-carb dieter (I lost 100 lbs.), I eat more healthy foods than anyone I know. I eat nothing white (flour, sugar, potatoes, rice, etc.). That means that I do not eat processed foods, the major culprit in our diet. I stick to Atkins products or other low-carb products without added sugars or hydrogenated oils. I do not drink sodas or flavored drinks. I eat plentiful amounts of low-sugar vegetables. I also eat low-sugar fruits. I only consume lean proteins. I exercise for at least 1 hour most days of the week (if at all possible). Low-carb living can certainly be a healthy way of life (if one can learn to effectively incorporate good carbs and not always fall back on induction).
As you can see, eating low-carb is a healthy way of eating. The problem with low-carb is that we get in the mind set that all carbs are bad. This is simply not the case. I have been trying to incorporate more carbs but it is difficult. I am still overweight and have not been able to lose weight no matter how hard I try. In that regard, you must also respect that some people have low-metabolisms and other issues. I also have thyroid issues and chronic fatigue.
I absolutely agree with the last line of your post. As a society, we need to place more of an emphasis on activity and less emphasis on food.