Which state shares a border with Canada?

Maine shares a border with Canada, making it the correct choice in this context. It is located in the northeastern part of the United States and has a significant boundary with the Canadian province of New Brunswick. This geographical position allows for direct land access between the two regions.

In contrast, California, Arizona, and Texas are all states that share borders with Mexico but do not have any boundary with Canada. California is situated on the west coast, Arizona lies to the southeast, and Texas is positioned in the southern tier of the U.S. The distinction is important, as it emphasizes the geographical relationships between states and neighboring countries, illustrating how borders play a critical role in political and economic interactions.