Secular Jew is an accepted description of a person who identifies as being Jewish but is Jewish in a cultural, nonreligious way. OK, I do understand that being Jewish is different than being "Christian", since there's a whole tribal identification and--like being mixed race--in a sense you are what the world will name you.
Christians aren't quite the same, though shared experience can create a tribal feeling for sure: church suppers (just listen to Garrison Keillor), nuns with rulers, bathrobe Christmas pageants, Midnight Mass--. And, since many of the US's immigrants are traditionally Christian, you have the whole food and whatever connected to the holidays. Tamales, stollen, a German pickle, clam chowder, or Taco Bell so mom doesn't have to cook, whatever it is, it is, and hallelujah.
My parents were both from the South though my dad was very evasive about what he actually believed and we weren't constant church goers, I was raised a Protestant Christian. Jesus watched every minute of my day and was very sad when I did anything wrong. My mother read a chapter of the Bible to me every night; I said the Lord's Prayer and long list of God blesses kneeling by bed, hands porperly folded, before I went to sleep.
Christmas was magic. Mary and Joseph, shepherds, Wisemen, and all the friendly beasts clustered around a baby while the angels sang. Every Christmas Eve I searched for the Star as I also watched for Santa and listened for the reindeers' jingling bells.
Peace on Earth and a Charlie Brown Christmas tree. I won't give up my claim on them.
That I don't believe in Christian tenets anymore in any orthodox or even unorthodox way, I believe deosn't matter--I cling to my right to my heritage. I collect nativity sets, sing Christmas carols when no one can hear (do unto others), remind myself that each person carries a spark of the divine and when I feed the hungry, clothe those without clothes, I serve whatever is holy in all of us. I should judge not and should remember that if I have two coats I ought to give one away.
For those who believe I still say I will pray for you. "To whatever is at the heart of all this and cares" may not be much of an address but I don't think it's the dead letter office and prayer is as good a name as any.
Tradition is good, love is even better, and stories that encourage children to believe that hope shows up in surprising ways, the angels sing of peace, and the scraggliest Christmas tree can shine like a star are, I believe, mine to claim.