To write a good thesis about this, you have to first put together what you know about early America and its approach to religion. Obviously, the American colonies were initially established, in part, as a way for people to freely practice certain religions. That said, they were extremely restrictive, with punishments for people who did not adhere to societal norms. Many undesirable behaviors were not just considered undesirable, but labeled as sin. The most dramatic example of this could be found in the witch hysteria that overtook some of the colonies and the executions and general destruction that happened surrounding the Salem witch trials.
Gothic literature evolved out of Romanticism and is really just an extreme form of Dark Romanticism. These literary movements began approximately a century after the Salem witch trials and its most famous American authors, such as Poe, were not writing for another century. Yet, the concept of sin and the psychological torture that goes along with the fear that someone will discover that a person has sinned, is a critical element in his works. The best example is the Tell-Tale Heart, where the narrator goes mad because of the fear of discovery. However, despite fearing that he will be discovered, the narrator does not seem to seek redemption. In fact, this is an element missing in many works of American Gothic literature that deal with sin. Therefore, we suggest a thesis that explores how the lack of a desire for redemption by protagonists in works of American Gothic literature reflects how American puritanical religious norms did not actually increase morality in people, but only the fear that they would be caught and labeled sinners.