Otherwise, it's just not a Christmas meal.
Here's an extract from the TV series Bottom, starring Rik Mayall and Adrian Edmondson (Source):
Similarly, in the US, there are certain things that seem to be mandatory as part of a Thanksgiving meal -- turkey, mashed yams, pumpkin pie and pecan pie. As I'm not going to be in the US for Christmas, what I'd like to know (if you're an American reading this) is, are there any other items that you would consider to be necessary for a Thanksgiving meal that I have not yet experienced? Are the required contents of the Thanksgiving meal set in stone (as they are in the UK) or is there a level of flexibility?
My other question is this -- is the fare at a traditional American Christmas meal the same as the fare at a Thanksgiving meal, or does a traditional Christmas meal in the US more resemble the British Christmas meal?