这两句话中，正确表达的是第二句，即He asked me if I was from the US.
英语主从复合句，特别是主句和宾语从句相互配合时，主句往往起到关键的主导作用，制约宾语从句的时态。主句如果是过去时，那么宾语从句中的谓语动词依据和主句谓语动词的先后关系，通常也应该使用过去时，即一般过去时，过去将来时，过去完成时等。
请看例句：
He said his mother was a nurse. (从句是一般过去时)
他说他的母亲是位护士。
He told his friend he would like to become an artist when he grew up.
（从句是过去将来时）
他告诉他的朋友，他长大要成为画家。
He told his teacher his uncle had been dead for years.（从句是过去完成时）
他告诉老师说，他的伯父已经去世好多年了。
因为前面asked
周末快乐！谢谢！
谢谢采纳！
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