Merry Christmas is a holiday greeting that is probably older than this country. Yet, it seems that in the last few years it is no longer politically correct.

I DO NOT CARE!!!

If that little two word term offends some late coming interloper, then so be it.
Yes, Christmas is a Christian holiday, it is also a national holiday in the USA.
If it was not for Christmas shopping, most retailers would go out of business. But, too many of those retailers proclaim Happy Holidays, or Seasons Greetings.
I do my shopping at those stores that still say Merry Christmas.