300 won't be that many for them, I feel like they're damn near everywhere. I have a mall near me that used to have two Gamestops, literally in the same mall. There's at least two other Gamestops in my city, and there's another one right around the corner from where I work (I commute to another city daily.)
I think GameStop could do wonders if it did more to cater to Retro fans. All of the new games are pushing digital distribution. Even if you buy a physical game now, it's not uncommon to have to download part of it when you bring it home. If Gamestop didn't destroy all of the packaging from all of the old games people used to bring in, I bet they'd be in a much better position now. I'd love for them to start pushing old out-of-print cartridges.
I googled it, there are 5830 in all countries they operate in. 300 isn't nothing, but it's also not a lot for them.
From what I know about GameStop, while living in a country that doens't have a GameStop (or at least, not nearby), they seem to be failing at their biggest strengths by trying to force only one (Second hand games as a market) while overlooking the others in favor of pushing aggressive consumer reward programs that I have never seen anyone speak positive of online.
Over here we have a store called Game Mania. Their biggest "shtick" is that they have a lot of merchandise aside from a lot of second hand games, usually stuff that's otherwise pretty rare to get (ie. they afaik currently have one of those special colored Wiis for sale as well as a few of the limited run 3DSes and the first time I went to them they had the Dark Souls 3 limited edition with the special thingies that were originally preorder bonuses, around 2 years after DkS3 came out) and official merchandise.
Like, brick and mortar game stores aren't dead, but if you run them like GameStop does, they might as well be. They have strenghts when it comes to selling rare things that you don't neccessarily have online (I don't have to be afraid that I get scammed for purchasing something in a game store the way I could get scammed by purchasing from the guy on ebay who is totes legit).