Another poster in another thread mentioned that the film set up the idea early about the danger of a warp core radiating earth, but that it was ignored after the big end crash. Did that seem to you like something that was left foolishly dangling?
I ask because I've read the end takes place well after this sequence, so you'd figure Frisco would be glowing or the bay would be leaking down into China if there really was a major accident happening (which also show why you shouldn't build starships at the base of a gravity well, but I digress.)
The idea that the Vengeance could radiate San Francisco with it's warp core has never been brought up in the movie, and when the ship crashed into the city it did nothing but destroy some buildings. Which of course still means ten thousands of death victims, but the movie ignored that completely.
However, that was just one brief scene that by no means justifies a tagline such as "Earth will fall".