I'm certain its NOT a SE problem. Data routing to the other data centers would be, naturally enough, different from the routing to the NA data centers. There's something wrong with the path the data takes between the ISP and the NA data centers.

People have gotten in by using mobile hotspots (which, presumably being a different carrier than their home internet, use a different pathway). People have gotten in using that WTFast software, which does not help PS3/PS4 users. That software finds a different path for the data to travel on, bypassing whatever section is bottlenecking/stopping everyone else.

Its an internet infrastructure problem. Whether or not it was put in place maliciously a few days ago is not something I can speak to, but from what I'm gathering on SE's boards here, its an internet problem, not SE's problem.