The arrival of millions of unassimilated immigrants is requiring America to abandon the old notion of a melting pot and turn itself instead into a gorgeous mosaic in which distinctive ethnic groups still manage to make a whole.
参考答案:
要点：本句是长句而非难句，因为句子中没有任何复杂结构。句子的`句架是The arrival of millions of unassimilated immigrants is requiring America turn itself instead into...。which引导定语从句修饰先行词a gorgeous mosaic。
译文：数百万未被同化的移民的到来要求美国放弃熔炉的旧观念，并把自己转化成一件努力将不同的种族融合在一起的璀璨的镶嵌艺术品。
