Although Jesus of Nazareth's birth was long associated in Scripture with the spring lambing season, His teachings spread far beyond the narrow confines of the Middle Eastern backwater that was His native land.
To make His Good News (Gospel) more palatable to Europeans the celebration of His birth was shifted to coincide with the long-established winter solstice celebrations, and during that time many non-Christian symbols of fertility, long life and rebirth became attached to Christianity. Among those non-Scriptural symbols now readily visible in 'Christmas' celebrations are the yule log, the tree, decorating the tree, sleighs and sleigh rides, holly wreaths and mistletoe. Oh, and don't forget the Mistletoe Kiss!
These symbols have traveled around the world in the years following the Great Expectation of the mid-1800s, when devout Christians took the Gospel 'to every nation as witness' (Luke 21:24). Mostly Americans and Europeans, these people believed that the Coming of One, like unto the Son of Man, was due some time soon, and with the expiration of the 2,300-year prophecy of Daniel later invoked by Jesus (Matt 24:14) and the 'times of the gentiles' being terminated by the Edict of Toleration, March 21, 1844, Christians around the world were inspired to leave their homes and bear witness to the truth of Jesus' life, teachings and death.
This provided the initial impulse for a wave of teaching that took with it, almost as an afterthought, the trappings of Christmas as it was celebrated by European Christians, zealous and selfless in their love of the redeeming Lord Who came in Sonship and divinity.
While some Christians over the years between 1844 and today have given their lives in the act of teaching, most of the 'missionaries' met with something more closely resembling success in teaching, 'converting' people to a Christian way of being, even if "the Christmas tree" was a coconut frond and snow was nowhere to be found.
Today Christianity, at least in its guise as some form, flavor, sect, arm or division calling itself Christian, can be found in virtually every nation in the world, even where it is actively oppressed. In most nations Christmas is at least another chance for buying and giving presents, getting off from work and enjoying a good time all around, even if the celebrants aren't too keen on learning Who the Christ was or reflecting the Light of His Word in their lives, today.
Christmas has become a multi-cultural phenomenon around the world, celebrated by many and excluding few.