Slightly related but I have always wondered wtf they borg must have thought in that first episode. They are going after this ship. Looks like its gonna go as easy as always. Then suddenly there is a bright flash of light and the fuckers spin away.
Pretty sure they were so into the federation for exactly that, because the Enterprise appeared out of nowhere, and then blasted itself back away. That's crazy looking tech from thier point of view.
Even if they did know about Q, there's really no reason to just assume it was him.
No, the Borg had already been probing the Federation and the Romulan Star Empire before that encounter.
Along the Neutral Zone various Federation and Romulan colonies disappeared, whole cities just scooped right up.
Q's interference may have caused the Borg to attempt assimilating Earth much earlier than intended, but the Borg were already on their way and they had no idea.
Due to Q's interference, however, the Federation was made aware of the Borg well before a Cube came on their doorstep.