We get a confirmation that the two pines or pine trees are the twin towers in the sequel of Back to the Future, part two, where we see the twin pines appearing again on a projection in a screen in Marty’s house.
His family gathers around the screen where the twin pines actually morph into the twin towers. So, the pines are the towers and the Twin Pines Mall is the Twin Towers Mall, which is why all the clocks showed 9:11.
But the appearance of the towers is not a random backdrop. One can notice the glowing torch lurking at the towers, which represents the Statue of Liberty, meaning that this scene resembles a recreation of New York City where Marty’s family has gathered to stare, at Ground Zero.
Of these three film characters staring at Ground Zero, there is one who is completely upside down:
But in the entire Back to the Future saga, this is the only time when an upside down character ever appeared. The hint being given is to observe from his perspective, by turning it upside down. When doing so, the twin towers are shown to be falling down. In the entire history of cinema, this scene of Back to the Future is the most literal depiction ever made showing the twin towers falling down:
So how is it possible that this scene would occur in a story that already contains a terrorist attack by Muslims at the Twins on 9/11 where the twins are the twin towers which then execute Hollywood’s best depiction of the Twin Towers’ collapse?