Look, it's really simple. Some people say "Merry Christmas." Others say "Happy Holidays." I have no idea what the proportion is. To the best of my knowledge, no serious research has ever been done on this subject. But regardless, it seems most unlikely that it has changed in any way whatever since Trump was elected. I suppose there may be somebody, somewhere may have felt intimidated from saying "Merry Christmas" and finally feels liberated. And probably somebody, somewhere has probably gone from saying "Merry Christmas" to "Happy Holidays" just out of defiance.
But perceptions can be very selective. If you feel that Christmas is under siege, you will notice every time someone says, "Happy Holidays" and feel affronted and overlook every time someone says, "Merry Christmas." And if you are convinced that the culture wars are going your way, you will notice every time someone says, "Merry Christmas" and feel vindicated and overlook every time someone says, "Happy Holidays."
And it is perfectly silly that I am even writing about this.