WASHINGTON — Tens of thousands of people from across the country arrived here Saturday to demonstrate against what they say is an ever-expanding intrusion of government in their lives in a culmination of a summer-long season of protests that began with an opposition to health care and grew into a broader dissatisfaction with Washington. A sea of people stretched along Pennsylvania Avenue from the Capitol to the White House on a cloudy and cool day, with scores of hand-written signs telling of their frustration. They sang verse after verse of patriotic songs like “God Bless America,” even as others shouted...