Re:.Bercik, Bercsik, Berzik, Berzsik
Your welcome Judi.
Born under Czechoslovakia's flag in Eastern region of Slovak Republic.
Were they not alive for 1930 census? That is the census that would have Na-naturalized or Al-alien.
Since they spoke "Slovakian" than the (re)search would be in Slovak Republic.
Take a look in this site for helpful, useful information.
Do you know religion of your ancestor?Sometimes that helps to point to a certain region.
Have you checked out EI manifests of BERZIKs?