Answer: The countries are in the order that Santa would probably visit them, based on the time zones around the world. The first (very populated) place in the world to start each new date is Christmas Island. So Santa's trip around the world begins at Christmas Island.
Question: Why are Alaska and Hawaii after Canada in the book, and not in the U.S. pages?
Answer: The United States is very large and contains several time zones. Alaska and Hawaii are in time zones that come after the rest of the US and Canada, so their traditions in the book come after the rest of the U.S. and Canada because Santa visits them later.