WASHINGTON (Reuters) - The only surviving copy of the 500-year-old map that first used the name America goes on permanent display this month at the Library of Congress, but even as it prepares for its debut, the 1507 Waldseemuller map remains a puzzle for researchers. Why did the mapmaker name the territory America and then change his mind later? How was he able to draw South America so accurately? Why did he put a huge ocean west of America years before European explorers discovered the Pacific?... ... Although the map conceals many mysteries, one thing is clear: it represents a...