It’s likely that if the video was shot in front of a green screen, it was so the president wouldn’t disrupt the important work being done at the factory. If this is the case, it does bring up several interesting questions about the stage-management of the presidency. President Obama has been routinely placed in front of stirring backgrounds dating back to his candidacy. The Greek columns placed behind him for his nomination acceptance in Denver was a perfect example of his reliance on visual imagery to convey an important, unspoken message to his audience.
It’s true that the president was in Detroit. And it’s probably true that it would have been wrong for him to shut down production for the sake of taping his weekly address. That being said, why go to the great lengths they went to (assuming this was a green screen composite) just to convey the image of the president sitting on a factory floor? What does it say about the White House’s desire to manipulate reality to evoke an emotional response from voters?