I would like to know your source for your previous statement that the Fall of Angmar in the film universe takes place very much later, well after the death of King Eärnur of Gondor. We do know that the discovery of the Necromancer in Dol Guldur marks the end of a "Watchful Peace" of four hundred years in the films, but how do we know that the Fall of Angmar, and not some other event, marked the beginning of that peace? .
You're right that this is not said explicitly, but it seems very much implied: we know that "The Watchful Peace" does not encompass just any military conflict, because there's been the Sack of Erebor and the Battle of Azanulbizar in the interim (not to mention the whole of
The War of the Rohirrim). So it must have been something pretty major, and since Sauron being present in Dol Guldur is a new development in the films, it seems very much implied - especially in the context of the discussion in the White Council scene - that this is bound with the fall of Angmar.
But this doesn't have to effect, realy,
anything in terms of beats of Tolkien's chronology. You can still have the Northern line becoming reduced to rangers, the Witch King defeated, retreat to Minas Morgul, mortally wound Earnur, and return to some remaining, long-besieged pocket of Angmarian force, and be finally defeated and incarcerated.
If there's something that might affect the chronology, it's Legolas' comment in The Return of the King, which implies Isildur was "the last king of Gondor." But this is seemingly contradicted by other comments made in the films and other elements of the films.