MOUNT VERNON, Va. — The people who were about to become United States citizens sat in folding chairs on George Washington's lawn at Mount Vernon on Saturday, 250 years after the Declaration of Independence. The sun beat down and the well-dressed crowd was a flutter of paddle fans stamped with American flags. Their families clung to the shade of the trees on either side, where one woman had two American flags stuck through her ponytail. “Well, good morning, everybody,” said Anne Neal Petri, the regent of the Mount Vernon Ladies' Association. “Good morning!” an excited crowd returned. “And Happy Birthday, United States of America!” exclaimed Petri. There were 150 people from 50 globe-spanning countries sitting in front of the small stage as they prepared to be sworn in as U.S. citizens on the July Fourth holiday and America's 250th birthday. Among them was U.S. Marine Sgt. Diakaria Sangare from Guinea, who attended in his pressed Dress Blue uniform with three medals pinned to his left breast. Sangare had served two deployments, and, like all assembled, had gone through the long