Jurgen Moltmann, well known for his reflections on the cross in the Crucified God, speaks of two crosses -- that of Golgotha and that of Constantine. The question is, which cross do we honor and lift up?
He notes that the cross of the Dream -- that of Constantine -- is the forbearer of the Iron Cross and Victoria's Cross. It becomes the foundation of a Holy Roman (Christian) Empire where there is "One God, One Cross, One Emperor, One Empire"
I don't believe that we are a Christian nation, as Americans, but let's for a moment say we are, which cross are we embracing in this idea? My sense is that most of those who embrace a Christian nation idea have a Constantinian or Crusading understanding of the Cross. The cross becomes the sword in this view.
The cross of Christ, however, is the one on which the suffering God meeets us -- so as to bring reconciliation to the universe.