I think it's just that the USA grows more corn than sugar cane due to it's climate. Thus its probably cheaper to use than importing cane sugar from overseas. I doubt at the time they knew the effects, but the over consumption, whether cane sugar or corn syrup would be the same.
Discussion
True. Just wouldn't be too difficult or expensive to import cane sugar from Latin America just like they do with Bananas and Pineapple.