My scrobbling statistics contains tracks with both "Bruce Springsteen" and "Bruce Springsteen & The E Street Band" as artists. I would like to unify those two as they essentially mean the same thing.
Basically, that is impossible. Last.fm does not offer any way to change your scrobbled data except for removing them.
However, there are advances to correct the global data, but the progress is very slow. I'm not sure if the artists are actually the same in your case. If they actually are the same, you can try and help correct the data.
I noticed there is a button for that in the UI sometimes, but it appeared only on a few occasions, so I'm not sure if it is displayed for you...