I have no clear idea where it was filmed. It could be anywhere that captured the essence and magic of Christmas, like a snowy village or a decorated city street.
It means that every Christmas is unique and has its own events, memories, or experiences that can be considered as a story. For example, a family's Christmas might have a story of a special gift that was given, or a time when a long - lost relative came to visit during the holidays.
I don't know who portrays Mia in that. It could vary depending on the specific production. Try looking at the cast list on IMDb or similar platforms for the accurate answer.