1865-1945 1945- 20thcentury american americannationalcharacteristics aspectpsychologique casestudies collectiefgeheugen collectivememory conditionssociales crises crises(aspectospsicológicos) crises(sciencessociales) general histoire historischesereignis history históriadosestadosunidos kollektivesgedächtnis local memory mémoirecollective nationalcharacteristics politiekecrises psychischestrauma psychologicalaspects psychologicalaspectsofcrises socialaspects socialaspectsofmemory socialconditions state unitedstates étudesdecas