On the surface that may seem like a perfectly rational standpoint. The reason why it's part of a superstitious belief is how that idea links up with other ideas. You are not arguing based on social data, but rather the abstract idea of what America is and for better or worse that's an superstitious argument.

In addition to resolving my own health issues, I have also raised two "twice exceptional" kids (gifted and learning disabled). The more gifted of the two was never identified by the public school system as gifted. He was always in special ed. My sons and I have walked away from a conventional lifestyle much as early immigrants walked away from the lifestyle of their native lands to come here. Europeans generally don't understand quite a few things about American culture, including the gun culture here. But Europe killed off most of its deadly animals a long time ago. We still have bears and wolves and poisonous snakes. We also have a lower population density, which means that if you get into trouble, you are more likely to have to deal with it yourself. There may be no one to call upon, much less police to intercede.

Additionally, studies show that Americans generally view more space around them as "theirs". One study found that some criminals in jail claimed such a large space around them as "theirs" that you basically couldn't be in the same room without them feeling you were in their space. This likely was a factor in their generally aggressive/violent reactions to things that wouldn't provoke others. The fact that Americans tend to claim so much more body space than Europeans or Middle Easterners may be part of why we are viewed as "the ugly Americans" -- it likely causes us to start conversations with people whom we think are "in our space" but who view us as butting in inappropriately. This view of or need for more space may well be due to physiological wiring, not just culture. It may well be part of why Americans prefer to spread out and create suburban sprawl rather than live in denser urban settings.

That is just a few examples. I don't think my assessment that Americans on the whole are likely wired differently from other people is simply superstitious. There is substantial evidence that we are misfits and loners and overly aggressive by the standards of more "civilized" cultures. We are mavericks and discoverers and explorers. This may be part of why we were the first to make it to the moon. Those traits are not simply pathological, with no good in them. But they do cause enormous problems in some settings. And there is substantial evidence that traits like that are rooted in physiology -- that "mental" differences are rooted in physiological differences (such as brain wiring).

FWIW: My medical diagnosis is "atypical cystic fibrosis". The typical prognosis for CF is that you get gradually sicker and sicker until infection has eaten away your lungs and you qualify for a lung transplant or die. I am not using diet and lifestyle to seek some kind of peak performance from a place of basic wellness. I have used them to stop being bedridden, close the hole in my left lung, get off 8 or 9 prescription drugs, get well enough to work a full time paid job for the first time in my life, and get well enough to live without a car and get around mostly on foot.

Peace.