应该去LV办一个复印件，然后到Nevada州务卿认证，然后就可以用了。

对于海牙公约成员国（中国去年加入）美国国务院只管联邦文书。结婚证是州文书，应该去州务卿那里办。

https://travel.state.gov/content/travel/en/records-and-authentications/authenticate-your-document/apostille-requirements.html?

see state and local document section

结婚证书，LV本县

https://www.clarkcountynv.gov/government/elected_officials/county_clerk/other_services/marriage_certificate_(ordering_marriage_certificates).php

州一级附加说明书（apostille) 

https://www.nvsos.gov/sos/businesses/apostille

然后就可以回国用了。