The script doesn't call for any visuals of the WTC's destruction, or use any audio from the event. It's implied strictly through dialog and some background SFX in the phone message. What we collectively witnessed, is not described as part of the imagery. Although the fact that we collectively witnessed it, gives the reference much of its power.
I don't want to trivialize 9-11, but it says something about many Americans' inability to see the scale of catastrophes - natural and man-made - that befall other nations, every year. There are people in Gujarat, for example, who would probably be grateful to have lost 'only' 3,000 some people, in their last earthquake...and people on southern Sudan, who probably wish that they'd 'only' lost 3,000 people, in the slaughter going on, there...
I don't want to trivialize 9-11, but it says something about many Americans' inability to see the scale of catastrophes - natural and man-made - that befall other nations, every year. There are people in Gujarat, for example, who would probably be grateful to have lost 'only' 3,000 some people, in their last earthquake...and people on southern Sudan, who probably wish that they'd 'only' lost 3,000 people, in the slaughter going on, there...