What you know as bologna or mortadella as produced in Italy is much more flavorful and more highly textured than bologna here in the U.S. See the Wikipedia entry:
[en.wikipedia.org]
Federal regulations governing production by national firms of this sausage stipulates no visible fat; the meat is ground extremely fine and is very light in color. The resulting commercial product is very bland compared to sausage prepared in small local delicatessens or butcher shops (charcuteries).
Similarly, most commercially-produced white bread in the U.S. is soft, white, and very bland. Not all white bread here is like this, but national brands selling "sandwich loaf" white bread are generally uniform in their texture and flavor (or lack thereof).
To say something is "as exciting as bologna on white bread" is to sarcastically emphasize its banality and blandness.
For examples, do a Google search for images of "Oscar Mayer bologna" and "Wonder Bread" -- you'll get the idea quickly.
[en.wikipedia.org]
Federal regulations governing production by national firms of this sausage stipulates no visible fat; the meat is ground extremely fine and is very light in color. The resulting commercial product is very bland compared to sausage prepared in small local delicatessens or butcher shops (charcuteries).
Similarly, most commercially-produced white bread in the U.S. is soft, white, and very bland. Not all white bread here is like this, but national brands selling "sandwich loaf" white bread are generally uniform in their texture and flavor (or lack thereof).
To say something is "as exciting as bologna on white bread" is to sarcastically emphasize its banality and blandness.
For examples, do a Google search for images of "Oscar Mayer bologna" and "Wonder Bread" -- you'll get the idea quickly.