You're welcome Jane !
No connection to your family. Someplace in the ancestors US document should be a place of birth. No going over the big water into Bohemia aka Czech Republic finding family information without it.
Who: what was the ancestor's first name?
When: did he come to America?
Was he naturalized citizen? Did he marry in America? Do you have any church marriage or baptismal record? Like I said, LOCATION, LOCATION, LOCATION.