Long before our girls were homeschooled, I tried to incorporate a study of Christmas Around the World into our Advent season. I must admit this is much easier to do in a homeschool setting. We simply have more time.
We are leaning strongly on curriculum found at teacherspayteachers.com by "The Teacher Next Door." It is called Christmas Around the World for Older Children. It is a great resource that includes mini-geography lessons as well as a story of Christmas customs from Canada to Japan and many places in between. We complete one country each morning and supplement with resources such as Countries of the World: An Atlas with Attitude and Maps. I have also found the picture book A World of Cookies for Santa very useful.
We also us the book Celebrate Christmas Around the World. I believe I have my mother to thank for passing this resource along to me. It covers a few countries not covered in the curriculum above. For those countries that are covered by both resources, this book provides crafts inspired by the country and often cooking projects. This book also incorporates Christmas carols. For example, this morning we studied Austria and learned how Silent Night was written in a small village in Austria. To supplement our discussions of Christmas carols, I use The Reader's Digest Merry Christmas Songbook, which provides a history of many favorite Christmas songs.
We use science curriculum from Elemental Science and I was thrilled when they sent me an email announcing their 25 Activities for Christmas Science. You can purchase this resource as a digital book and download it immediately for use. So far, my girls have enjoyed observing the difference in how a candy can melts in cold versus hot water. They have also built Lego mazes.
I am sure other resources will pop into my mind that I have failed to mention here and I will attempt to update these recommendations throughout Advent. I hope this provides a nice starting point for your own planning.