http://beijing.usembassy-china.org.cn/acs_notary.html
Authentication
Please make sure the documents you bring to us have already been authenticated by the Notarization and Authentication Division of Consular Affairs Department of the Chinese Ministry of Foreign Affairs. The telephone number of the Notarization and Authentication Division is (8610) 6588-9761.
一般三级认证是私人签字的声明合同。中国法院的判决,如果是盖章的原件,应该不用去公证,可以直接去中国外交部认证后,然后到美国领事馆认证。你可以向中国外交部认证机构打电话询问。
美国外交部如是说:比大使馆说得详细一些。
http://travel.state.gov/content/passports/english/abroad/events-and-records/divorce/divorce-legal-issues.html