Probably sooner, IMO. Absent radical life extension, even 200 years from now there'll be nobody's left who remembers the time before deepfakes, and history will be brought into doubt.

Though bluntly we've always had nationalistic narratives contaminating what's "approved" in school, both with literature and history. Stephen King could be anything from mandatory to forbidden for any reason at the same time in different places, even on that kind of timescale. The USA may cease to exist as a singular coherent entity, and it may be two or more successor states in parallel who have a culture war with each other over if Stephen King was real or not.

Good question. No. Since the press was invented, our records have improved tremendously, partially because of the low cost of maintaing them. However, we still have detailed records from many eras, tracing back at least 3000 years. The egyptians had archeologists, let that sink in.