Can the polarization between Democrats and Republicans in the U.S. be reversed?

[Angrboda]

The past included a civil war.  The reconciliation resulted from the the understanding that the preferred path for one side is blocked by overwhelming military force proven able and willing to win.

I strongly suspect that the reconciliation in the Civil War is not the only such example in world history, but in any case, you have the arrows reversed. The people who made concessions were those who had triumphed militarily and thus had no need to make concessions, not those who might have been cowed by their prior defeat. So you have the history here upside down.