-See the following I cited at: http://www.china-embassy.org/chn/lszj/hzlxz/t1234455.htm#L3
Because the child's mother is still a Chinese citizen, your child should still be qualified for 旅行证. But if the child's mother also becomes a US citizen (i.e. both parents are US citizens), then the child has to apply for a Chinese visa, no more 旅行证.