According to an exhibit at the partially reconstructed New Synagogue of Berlin, which we saw in 2005, Einstein only ever once entered this building – to play in a concert on his violin. He was resolutely secular and never belonged to any synagogue. Needless to say, this was of no interest to the Nazis, who hounded him out of Germany with a price on his head.
The exhibit we saw, along with many other celebrations, marked the centennial of his great 1905 physics papers. Now the Germans claim him, and well they might, as he's one of the greatest scientists ever, as well as a humanitarian leader.
Of interest in the aspect of secular Jewish identity: although Einstein evidently stopped believing in God at around age 12, he was a proponent of the founding of a Jewish state in Palestine and an active Zionist fundraiser. He contributed to developing the Hebrew University of Jerusalem.