She said that he had gone to America the year before.首先last year变间接引语the year before
完成时要看两种动词：点动词如come,go,leave,arrive接具体的某个时间点表示“到这个点的时候,已经出现某个结果”这句话中,“到去年为止,他已经走了”
还有一类延续动词,就是那些可以一直做下去的动作,要加一段时间for 5years/a few minutes/a period等等.比如,He has studied math for 3 years.We have worked for about an hour.
因为主句是过去时,而她说这句话的时候他已经走了,所以从句用过去完成时