He spent sixty years explaining how the United States became a democracy, and he died weeks before it turned 250. Gordon S. Wood, the most influential historian of the American Revolution, was born in Concord, Massachusetts, in 1933, and killed by a car in Rhode Island on June 7, at ninety-two. He was revered by many, resisted by others, ignored by no one. He even reached the movies: Matt Damon’s character skewers a pompous Harvard graduate stud…