I grew up in mid-Twentieth Century United States. I always lived in areas which were mostly Jewish, but I never had a doubt, no doubt at all that the United States was at heart, mind and media a Christian country.
As I remember, the early history and its stories of religious freedom were about various Christian groups, not full religious rights for all religions, Hindus, Muslims, Jews and any others. We lived with other Jews to feel more comfortable. The local New York City public schools were closed Rosh Hashannah and Yom Kippur. No other Jewish Holidays seemed to be known. We weren't religiously observant.
In neighborhoods like ours, the schools kept the "winter holiday celebrations" pretty G-dless and sans Jesus, too. We sang about snow, Santa and dreidles. The only "religious" song was "Silent Night," which most of us Jews didn't quite understand. Easter, I associated with bonnets and decorated eggs. I never caught onto any religious message about it from the TV shows; it remains an enigma. Yes, television was the great educator and assimilation tool.
May father learned English in school and both my parents learned American customs and values there. But I learned from the TV.
As a teen I felt that I had to choose between being Jewish and being an American, Being American meant accepting christian customs and priorities. In Great Neck North, NY, I had a teacher who would complain that the Jews ruined things for Great Neck. I was amazed and asked what she had meant:
"Before the Jews came, we had such beautiful Christmas pageants."