How can an American Citizen File for Divorce from Estranged Wife living in Guyana?

My boyfriend is legally married to another person in the country of Guyana (which happens to be my birthplace). He and his wife have been estranged for almost 3 years and he (the American Citizen has never claimed or reported his marriage here in the States). He seems completely confused as to how to begin a divorce process without having to travel overseas. The laws governing marriage in Guyana are quite archaic.