Rorschach's social worker is very prominent in the scenes of the NYC explosion.

You bring out good points about the changed ending though. A lot of the gore of the original explosion is toned down -- due to the changed nature of the attack, and probably because you can show the superheroes bloodily killing and maiming others, and you can show a destroyed New York, but showing bloody maimed bodies in a destroyed New York is probably (rightfully) judged as a still too triggery for people post-9/11. So the movie trades out the gore to underline those scenes with post-9/11 horror.