Crank 2 picks up pretty much from where Crank left off. In fact it picks up from exactly that point. That itself doesn't make a lot of sense, but then this is the story of Chev Chelios and much like a an episode of Dallas, you know your audience will accept it all at face value.
So what we have here is a crazy ass showing of stunts, mayhem, chaos and bad language (well offensive actually) and story telling of the up most stupefied. Possibly everything that Postal wanted to be but could never be as it was hampered by Uwe Boll and didn't start the legendary Statham (I am yet to see the Boll/Statham collaboration though and didn't I say that about Crank)
So as is the tradition of popcorn movie making, the sequel takes all the extreme elements of the predecessor and expands them into an even more mad movie, almost as mad as this and well madder than the opening 15 minutes of Dead or Alive (which in my head I'm sure was mad). You want highbrow subtext then look elsewhere, but........
.......life, film, video game, film...life???? There has to be a thesis in there somewhere, in fact if the opening frame of the movie had been Stathams eye blinking open then we may have had oscar worthy material here ;)