Bart Simpson once said that "“Christmas is the one time of year when people of all religions come together to worship Jesus Christ.” Some people would say that he is half right. Many people celebrate Christmas (96% of Americans do), but some of them don't do so in order to worship Jesus Christ. As of late, there has been a lot of arguing over who "owns" Christmas and whether it has been changed into a secular holiday rather than a religious one. The most recent White House Christmas card is only a small part of the ongoing debate about Christianity and Christmas and how intermingled the two should be in public spaces. (Note: The White House Christmas card is not funded by American tax dollars, but by private contributions to the Republican National Committee so it is not an example of communication with an obvious religious message being spread via public funds. It is, however, communication with a presidential seal on it that carries a religious message clearly and intentionally marking it as a governmental communication with religious content.)
As is often the case, how people perceive the issue (of the Christian or secular nature of Christmas in this case) is a matter of perspective. People tend to view Christmas through the prism of their own beliefs (or lack thereof). Christians feel Christmas is a very Christian holiday. They see nativity scenes, hear songs which praise God or the birth of Jesus, and talk about church attendance numbers and the percentage of Christians in the U.S. Non-Christians feel it is a secular one. They see Santa Claus, cite the pagan roots of many Christmas traditions, and hear songs which are festive (e.g., Jingle Bells), but in no way reflect religion. The truth can't be found in subjective perceptions, anecdotal bits of information supporting one side or another, or in wishful thinking that reality will bend itself to suit one side's will. "Truth" is in objectively-obtained statistical information which reflects the whole rather than its parts, particularly when the parts are so heavily influenced by their own agendas and biases.
Finding objective data regarding this issue is actually quite difficult. Most polls tend to be conducted by groups with a vested interest in one outcome or the other. Such groups usually poll small and highly-biased samples. Christians tend to poll church goers. Atheists tend to poll from organizations or via web sites which attract like-minded people (e.g., scientific web sites). Fortunately, there are some organizations which conduct such polls without bias and that use scientific sampling methods.
Gallup has been doing such polls for decades and, despite some rather ignominious failures ("Dewey defeats Truman"), has been quite reliable, particularly in terms of predicting the outcomes of presidential elections. Fortunately, their techniques have been refined since their most famous failure and their results are reliable within a predictable margin of error. The margin of error, for those who aren't familiar with statistical information, means that the results can be wrong either either way by a certain percentage. In the case of most Gallup polls, the margin of error is plus or minus 3%. That means that a poll showing an opinion is held by 45% of people can be believed to be held by as few as 42% or as many as 48% of people, and that is quite unlikely that it is held by less than the lowest or more than the highest of those percentages.
In order to address the question of how "Christian" Christmas currently is, I decided to turn to the Gallup poll results from a 2005 survey. It's not only a reasonably reliable polling agency but also one of the few (non-biased) organizations that asked the questions I was interested in having answers to. A Gallup poll that asked the question, "thinking of the way you personally celebrate Christmas, is it a strongly religious holiday, somewhat religious, or not too religious," showed that Christmas is considered a "strongly religious" holiday by 47% of people in the United States overall. As a good example of how perspective introduces bias, Christmas is seen as "strongly religious" by 80% of regular churchgoers. If they were to believe everyone views the holiday as they do, they'd believe nearly everyone celebrated Christmas as a "strongly religious holiday."
Before anyone concludes that this is evidence that religion is being removed from Christmas, keep in mind that 30% of those polled said that their Christmas celebrations are "somewhat religious". That means religion is part of 77% of celebrations of the holiday. That means 23% of those who celebrate Christmas do so with no or very little religious component. Clearly, there is little danger (for the time being) of Christmas being celebrated as an entirely secular holiday by the majority of Americans.
The interesting thing to me is that people find it necessary to argue over the validity of the Christian aspect of a Christian holiday in the United States. Only in America would people argue for the secular hijacking of one of a religious group's most sacred holidays (the only one which is held in greater esteem is Easter). It's not that people don't want to celebrate Christmas because they are not Christians or are arguing to reserve their right to observe the holiday as a secular one, but rather that they don't want anyone to associate the holiday that celebrates the birth of Jesus Christ with religion.
Mind you, I have no problem with people choosing to celebrate Christmas as a secular holiday. After all, I'm not a Christian and I celebrate Christmas, but I'd never feel that the holiday should be or has been divorced from it's religious connotations because I have personally abandoned those aspects. I see the debate to strip Christmas of it's religious elements as the absurd extension of political correctness in the U.S. where nothing can be referred to in any way which may make any group feel the slightest bit uncomfortable (no matter how far-fetched their concerns are) and a backlash against the (undeniably) inappropriate influence of the religious right on conservative politicians. However, I think that trying to pretend Christmas is no longer a Christian holiday isn't going to accomplish anything.