Former Presidents Biden, Obama, Clinton, and Bush shared messages marking America's 250th birthday.Biden: “The 250th anniversary reminds people that democracies depend on certain basic rules. Democracy is dictated by the rule of the Constitution.”Obama: “Remember what's best in us. The basic principle upon which this country was founded is that we don't have rulers, kings, monarchs, or aristocracies—we have citizens.”Clinton: “America is bigger than anybody's personal hopes and dreams. The count