原句应该为：america and americans were prosperous beyond the dreams of the europeans and asians whose economies the war had destroyed.
美国及其国民的富裕是那些经济遭到战争破坏的欧亚诸国做梦也无法达到的.
分析：句子的主干结构是america and americans were prosperous,beyond the dreams of the europeans and asians作全句的状语.whose economies the war had destroyed作定语从句修饰the europeans and asians.而the war had destroyed作economies的后置定语,即“遭到战争破坏的经济”