Economic collapse. I don't think it is "imminent" at all, but I do think it is inevitable since no will at the fed and many of the state govs to do anything but make it worse. Can be many possible tipping points - most likely to me is hyperinflation caused by inability to borrow the huge sums to keep funding everything. One the entitlement class stops receiving their free stuff, look out. While a race war may also be possible, I see this mostly confined to the larger cities.