I have yet to see any evidence that it exists ... but if it did exist, I can't for the life of me understand why advocates of "America as a Christian nation" would have a problem with it.*
War on poverty, war on drugs, war on terror -- pretty much every "war" we see that isn't, you know, an actual international military conflict and solely such a conflict, results in more of whatever is being warred upon.
If there's really a war on Christmas, we can expect that within a few decades at most more people than ever will be celebrating Christmas as opposed to some other holiday, or generic "happy holidays/season's greetings" or whatever.
Am I missing something?
* I exclude, of course, Christians who consider Christmas to be a thinly veiled pagan holiday rather than a genuine Christian celebration. Yes, there still are some of those around.