Chazon Ish-1930 Poland/Russia=Babylon

I read in the Artscroll notes of Kesubos-it says on the Gemara ‘just as it is forbidden to leave Israel for foreign lands, so it is forbidden to leave Babylon for foreign lands-The Artscoll notes there say it says in Teshuvos Chazon Ish that Poland with the saintly Chofetz Chaim and many other gedolay Torah (may) have the law like Babylon-The Artscroll continues–see there for the status of Russia aswell (possibly Belarus, and Lithuania).

Can someone find this Teshuva and tell me what it says in full.

Thank you!