I think it could either work as the complete focus of a collaborative writing experience/message board (so effectively the equivalent of a the SCP wiki, with contributors only expressing themselves in the form of recorded material), or indeed as a fun mental exercise in the background of another Alternative Universe game where it's not the focus (so the equivalent of some of the pop culture plays that appeared in Watchmen and the like).
Having something between the two (i.e. playing a game as critics) would to me be fairly risky, both because I don't necessarily see where you'd get your drama or plot from, and indeed I would worry that most of your player interaction and conflict would be PvP arguments about random bits of canon and I can't honestly claim that would seem particularly attractive to me! You could potentially put it as a slice of life game set within a publishing house, but then again, I'd say that the pop culture would be the background and the in jokes rather than the focus of drama itself.
What I would probably add is that:
Wildcard:
1.) Outside of pop-culture the history of this alternative universe is like ours when it comes to historical events and attitudes towards them.
might be a bit of a tough ask given the intertwining of pop culture with political/historical events. If you're not allowed to mention IRL media, then history potentially takes a different turn unless the in-game media is basically the same thing with a different name (so the protest songs of Dylan Bob, the cultural effects of Space Meander etc.), and you also then have to decide where the barriers sit for people who transcend the media/political spectrum (so how do you justify the Reagan presidency if he wasn't a semi-popular actor?)
I'm not saying it's impossible, and indeed if you wanted to take the inspiration from the Player Two Start Approach, I think you could write a really interesting game set from that divergent point and have new players/characters every generation building on the canon of the previous one (with the changes in media increasingly affecting global politics and culture afterwards until it diverges massively from our own), but whether that'swhat you're looking for is another question!