Assembly in the USA makes sense for big bulky things where the savings of overseas assembly isn't enough to offset the cost of shipping. PowerMac and Mac Pro towers and Xserves were (are?) assembled in Elk Grove, California (near Sacramento) and somewhere in Texas. If Apple decided to do the same with the new iMac for some reason (Mac Pro demand probably isn't keeping the plants very busy, and Xserves are gone) it wouldn't come as a huge surprise.
12/2/12 at 7:50pm