because its a tradition
Christmas Eve
In Australia, many people put up their Christmas tree on the 1st day of December. It varies. There is no tradition in Australia for when to put up the Christmas tree. Some people put it up early in December, while others put it up at various times in the weeks preceding Christmas. Some may leave it until Christmas Eve. There is truly no tradition.
It's just a tradition, you are not required to put up a tree if you don't want to.
Representing the star over Bethlehem, it arrived atop the Christmas tree after Christianity "borrowed" paganistic tradition.
People put up their Christmas trees at different times. It depends on which tradition they follow or personal choice. One tradition is to wait until Christmas Eve day and leave it up until the day after Twelfth Night. One reason for this tradition is to spend the Advent season preparing for Christmas, then put the tree and decorations up to celebrate the feast of Christmas. Another tradition is to put trees up on Saint Nicholas Day, December 6th. Another tradition is to put the trees up on Immaculate Conception Day, December 8th. Then there is the tradition of setting up the tree on December 13th, 12 days before Christmas.
If I understand your question correctly..... The German tradition is to put up the Christmas tree on Christmas Eve. Once that is done the presents are put under the Christmas tree. Children see the tree for the first time at "Bescherung" the gift giving on Christmas Eve. Not sure how many families still stick to the above tradition.
Traditionally it is the 23rd December, Christmas Eve.
It came from Martin Luther King as one Christmas he looked up at the stars through a cedar tree and after he saw the amazing sight,he took the tree inside and he and his family decorated it by put candles on it to represent the he saw.That is how the tradition of decorating a tree came from.
Thanksgiving
Yes, they have mostly Christmas trees. There is also a tradition where they have a small boat instead of the usual tree, but that's sort of oldfashioned now.
Some people still put trains under the tree every year. Though the tradition of trains under the tree remind people of simpler times, its not a popuar tradition any longer.