One of the things that incompetence in high places can botch up is historical commemoration. This is the 250th anniversary of independence. Then came the articles of confederation. Then came the constitution, and with its ratification by the people in the states, the present republic began. A nation can be defined by ethnicity or political structure, depending on when the term was first used; clearly in this case, we look to the latter, and so the nation began with the ratification and the republic. (Else, we're using "nation" to describe an ethnically heterogeneous population in a certain place, irrespective of political structure.)
(I think the Chief Justice might have been obliquely saying as much in his discussion of the Declaration with respect to the organic documents in last year's year-end message.)