Having never had kasseler bread, I can’t really comment on the similarities, but after googling around a little it’s probably in the same ballpark. These sort of deli sandwiches are usually served on (what we call in America anyway) “Jewish rye” bread. Just sort of a soft, light rye bread, often with caraway seeds in it (personally I tend to think of the seeds as sort of the defining feature of a Jewish rye) and I couldn’t find any mention of kasseler having caraway, but I also didn’t exactly do an exhaustive search for recipes.