My fuzzy memories of America’s bicentennial encompass fireworks, plays about Paul Revere and a country, even amid the turbulent 1970s, excited to celebrate together. Our semiquincentennial brings a different vibe, with political polarization blunting the idea of a common commemoration. That’s unfortunate, because the United States, founded on an ideal rather than a creed, remains unified around the concept most core to who we are: the American Dream.