Without John Proctor, there is no play. He is the reason Abigail Williams is in the forest at night "conjuring spirits" with Tituba and the other girls. It is for his love that Abigail does everything she does. Without him and his complicated web of infidelity, guilt, and moral compass, there is no play.
He is considered an American hero because he stands up for what is right. He does not buckle under the weight of authority, even when it becomes painfully clear that he will not win. He is ultimately, the underdog. A clearly human (imperfect) creature with whom we all are able to relate on some level--through his complicated relationship with Elizabeth or his lusty diversion with Abigail or his indecision as the right course of action in the political dealings of the community. He struggles, and we struggle with him. In the end, he dies for his belief and for the worth of his name which is all he has to leave his children. He refuses to give in to something he knows is a lie, and he dies alongside another hero, Rebecca Nurse.
John Proctor is the main character, or the Protagonist of The Crucible. He is at the center, along with Abigail Williams, of the witch trials hysteria. Even though Proctor attempts to stay out of the middle of the fear and paranoia that grips Salem, he is dragged into it by Abigail's accusation against Elizabeth Proctor.
Proctor's affair with Abigail has set the entire accusation process in motion. It is because of Abigail's desire to get back together with Proctor and to eliminate his wife, that she takes control of the group of girls leading them in pretending to see spirits in court.
She advances her plan to get rid of Elizabeth by accusing her of witchcraft. Once Elizabeth is arrested, Proctor has no choice but to go to court and fight for her life.
"When the accusations fly at the trials, he is determined to tell the truth, even if it means criticizing and antagonizing the investigators. His determination to expose Abigail's false accusations eventually leads him to admit his own adultery to the court."
John Proctor is considered a tragic hero, and an American hero, because he makes the ultimate sacrifice, giving up his life for his beliefs.
Proctor surrenders his earthly life rather than give up his name and reputation in Salem. He gets some of his dignity back by confessing his sin with Abigail and then decides to protect his family by not saving his life by confessing to witchcraft.