Earlier I referenced Abbas Milani's article on myths the Iranian regime promulgates and perhaps still believes in about the history of the "Great Satan," especially the supposedly crucial role the U.S. played in the 1953 that toppled the democratically elected Mossadegh and brought in the Shah. Milani contended that the role of the U.S. was minor. As I noted, former British parliamentarian and my friend Eldon Griffiths agrees.
Here, thanks to a commenter, is a point-by-point rebuttal of Milani's article, c0ontending the U.S. role was key in 1953. I'll need to read them both more carefully side-by-side to have a more considered opinion, but present both for your consideration.
I'm not sure how much that history impacts the current situation. At this point, as persistent as the protesters have been -- more so than most observers expected, I warrant -- the regime still seems to have the upper hand with fairly well calibrated violence. Is the regime nonethtless vulnerable? I think so, but don't have any special insight on timing.