A fourth season TZ ep is partially about the Lusitania and its greater than Titanic historical importance. Books like "Did these stories really happen" and "Battle at Sea" prove the Lus had great historical significance.
The Lusitania had a greater impact than the Titanic. While both are tragedies, the Lusitania cooled relations between Germany and the US. It also created uncertainty with Britain. Plus it sank in less than 20 min.