Isn't that fascinating! It had never occurred to me that American law did not consider the written word to be pornographic.

Here it is the explicit description of, or the depiction of, sexual activity. And if that includes an under 14 year old it is paedophilic, whereas if it includes a 14 or 15 year old it is a slightly lesser category, but still illegal as either an image or written explicit description - the legal age for pornography to depict or describe is 16.