Really, could the Borg's interest in the Federation be because of Q's actions in Q Who?
Well it was the Borg who were behind the mysterious colony attacks in the TNG s1 finale
The Neutral Zone, so really it wasn't like
Q Who was the Borg discovering "hey there's this thing called the Federation in the Alpha Quadrant" to begin with anyway.
So that's 1.
Then as the Trek franchise expanded you have 2, Voyager establishing the Hansen's had contact with the Borg and were eventually assimilated in the 2350s (
Q Who takes places in 2365)
3. Voyager
Infinite Regress later established the USS Tombaugh was assimilated 13 years prior to the episode (2375) making it 2362. Again before
Q Who took place.
4. Enterprise
Regeneration has the leftover First Contact Borg sending out a signal to their 22nd Centry Delta Quadrant brethren about Earth, but it will take 200 years to reach them anyway.
So I'd kinda look at it as a whole as maybe the Raven incident occured first making them aware of us, then maybe recieved the 22nd Century tranmission and were like "hmm let's go check these guys out."
The Tombaugh was probably a long range deep space vessel they encountered and that got them more interested so they decided to go check out some outer colonies around the Federation (weren't Romulan colonies destroyed too, its been ages since I saw
The Neutral Zone.) And then after the Q Who incident of a prominent Federation vessel been that close to their space they went "ok let's send out a Cube right into this Federation/Earth then" (obviously leading to Best of Both Worlds)
Or maybe they recieved the ENT transmission inbetween Q Who and Best of Both Worlds and that's what made them want to go for Earth. Either way the ENT transmission is almost irrelevant anyway; I think they would have gone for Earth with or without it. It's just a cool thing for the end of the episode.
But that's how I'd generally look at it anyway