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France's longest border is with Brazil
(lemmy.world)
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They also have a border with Canada at St Pierre & Miquelon.
The map only includes land borders. St Pierre and Miquelon are islands, so they have none. France has several small islands scattered around the world as legacy of the French Empire which are also absent from OP's map for the same reason. Saint Martin on the center left is a notable exception, since it's divided in two between France and the Netherlands.