How does The Crucible compare to actual historical events like the real Salem Witch Trials and the Red Scare?
One way to go about writing such an essay would be to contrast events and people as portrayed in The Crucible to how they are viewed by historians, and how they are described in the primary sources that survive from the trials. You can find primary sources associated with the trial, including transcriptions of the proceedings of the Court of Oyer and Terminer convened for the witch trials, at the Salem Witch Trials Documentary Archive and Transcription Project, linked below. For a brief overview of how historians have interpreted the Salem Witch Trials, see the article by Mary Beth Norton linked below. Norton's book In the Devil's Snare is a wonderful scholarly book about the trials, and there are many more—it has been very widely studied.
As far as the Red Scare, a good essay would obviously consider the historical context of The Crucible. It was written at the height of the Red Scare after World War II, with the House Un-American Activities Committee routinely dragging intellectuals, government officials, and most famously Hollywood screenwriters into chambers to testify about the supposed threat posed by Communism. Many of Miller's friends had their lives ruined by these accusations, and a good essay might consider the ways in which the hysteria in Salem paralleled the anti-Communist frenzy of the early 1950s. You can find analysis, critical essays, and other information about The Crucible, its author, and its historical influences here on eNotes (again, see the link below).
Either of these approaches would make for a strong essay. You could perhaps take it to the next level by considering why Miller, a twentieth-century playwright, portrays events as he does (after considering how his play deviates from historical accounts and the primary sources). How did the political climate of the times make the story especially compelling, and what contemporary figures might compare to John Proctor, or the Reverend Harris, for example?