That's exactly how deal with these changes in my headcanon too.
And it also perfectly explains the changes to the Borg from TNG to FC/VOY.
I believe before FC no one beside of Guinan (and possibly some El Aurian survivors who also kept their knowledge to themselves) knew anything about the Borg and Annika Hanson as well as her parents were never assimilated.
Right! People act like the Borg drone sending out a signal was some type of predestination paradox, but (since I don't believe in those), it makes more sense to me that the Borg became more aggressive, and headed towards Earth a lot quicker, and inflicted a lot more damage along the way, because of the butterflies / timeline rewrite caused by First Contact.