The spoke Slavic but were not Czech.
The word Czech seems to be used incorrectly by many American descendants.
Remember, it was A-H
http://users.erols.com/mwhite28/austhung.htm up to 1918.
After the fall of A-H empire several new countries were formed and one was Czechoslovakia [full map}
www.cgsi.orgAfter WW2 Ruthenia went to Soviet Union now Ukraine. In 1993 Czechoslovakia separated into Czech Republic and Slovak Republic. Your ancestor was from Slovak Republic.
SSDI - SS-5Form is purchased from Social Security, Baltimore, MD.
http://www.genealogybank.com/gbnk/ssdi/