Warschau is the German spelling for Warsaw, Poland.

If he sailed from a German port (e.g., Hamburg, Bremen) then the German clerk likely used the German spelling of the place name.

The Resslince spelling is not a Lithuanian one for the place name.

Have you ever used the Slownik Gazetteer. See

http://stephendanko.com/blog/1587

Slownik lists thousands of place names (using the Polish spelling) including many in Lithuania.

What do the U.S. Census entries for them list as their countries of birth?

Tom S.