Hmm. I'll admit I'm not up on my canal history, but this encyclopedia entry about the canal's history doesn't reek of imperialism to me. Especially since, as of 1999, the Canal is under Panamanian control. It sounds to me like the U.S. pretty much purchased all the rights along the way to make the canal happen.

Another quote I saw in my googling said "the U.S. has at least as much right to the Canal as it does to Texas" and that seems about right to me. The fact that we've since released control to the Panama government would seem to underscore our lack of interest in having it be part of our "empire."