The correct answer to this open question is the following.
The juxtaposition of these two days -Thanksgiving and Black Friday- reveals the following about the American identity and who we are as a society.
First, Thanksgiving, the most special day for the American people. A day in a year in which family gathers together and say grace and express gratitude for what they have.
It is sad that there is one "official day" established to express gratitude and celebrate. Every single day is the perfect time to thank for what we have and for the fact that we are alive. And here comes the next part of my answer, Consumerism.
As families gather together, happy, in the family environment, marketing and consumerism take advantage of these happy moments and moods in the American family to "invite" them to move the economy and spend as a way to prove their prosperity. And then we go, "happily" to shop, shop, and shop. It does not matter if we need the things we buy, or not. If it's on sale, it is a good time to shop.