In 1993 Czechoslovakia separated into Czech Republic and Slovak Republic.
The US documents should provide you with his place of birth.
DULIN in 1995 in Slovakia in these locations:http://slovniky.korpus.sk/?w=dulin&c=m982
An ALL site for research in Slovakia:www.iabsi.com/gen/public
Dulin, Jozsef A. Szlovinka 18 1885 1903
Dulin, Jozsef Kissaros 18 1886 1904 www.ellisislandrecords.org