I would say Italy. Rome to be precise. It's a bit of an opinionated question/answer as christians believe christmas is the celebration of Christ's birth, on 25th December, whereas historians will tell you this is incorrect and christ was more likely to have been born around September/October. Christmas day (the 25th) is in fact a Roman-originating tradition in celebration of one of their gods.
As far as I am aware Christmas is a Roman Catholic/Christian adoptation of the pagan/Germanic Winter Solstice. Just as much as Easter is an adoptation of the pagan Spring Festival (held the first Sunday after the first full moon after 21 March, or something like that. How pagan can you get?).
Father Christmas can trace his roots back to his Germanic times too!