WASHINGTON (AP) — When the nonprofit organization planning America’s 250th birthday celebrations decided it wanted an ornament to commemorate that milestone in history, its leadership knew just where to turn for guidance. America250.org worked with the White House Historical Association, which, since 1981, has sold a popular Christmas tree ornament honoring a president or a key White House anniversary. More than 1 million of those ornaments are now sold every year. The two groups worked