American Exceptionalism begins with food?

In Butler's piece, Becoming America, a bold assertion is made that "This American "exceptionalism" stemmed directly from dietary improvements that began at colonization and, for Europeans, continued throughout the colonial period."
 Now I'm hardly the man to research the foundation of a claim as bold as this, but this is probably a fairly reputable source (I'm assuming because I was assigned to read it) so if we suppose for a moment that this hypothesis is true, then this claim becomes even more troubling. Never mind that this book is claiming American exceptionalism isn't derived from our heart, grit, determination, passion, patriotism, and all around better-ness because we're from America. Never mind that this statement claims the only reason we're the greatest country in the world is because of the food we ate. Never mind these two sarcastic remarks on my part, because that's not what troubles me.
What troubles me here, holding that this assertion is true, is that if food is what lead to the America's prosperity, the future is definitely not looking good for America right now. Heart disease as a result of poor diet is nothing short of an epidemic. The government subsidizes products like corn that are then turned into unhealthy substitutes for natural products (think high fructose corn syrup) and the health of our nation declines. And why shouldn't we make every product under the sun out of corn? Subsidies have certainly made it profitable to do so. The government is indirectly subsidizing the poor health of Americans and at a great cost. Not only is Americans unhealthiness leading to a decrease in productivity, but as a result of their unhealthy ways as a whole, American's pay the most in the world for healthcare and for healthcare that doesn't perform nearly as well as many other nations in the world.
But the inefficiency of the American healthcare system is a topic for another day. The fact is that people that don't eat right become unhealthy. Unhealthy people get sick more often. People that get sick more often pay more for healthcare. Do you see where I'm going with this?
Food can be an interesting sociological standpoint from which one can look into a society. If we assume that Butler's statement about the importance of food is correct, things aren't looking so good for American "exceptionalism" right now.