If the other groups you mentioned were perceived as a threat to the U.S., I'm sure that Bush would be just as interested in them as in Iraq. The U.S. does not have the means to right every wrong in the world. Attempting to do so would spread our military way too thin to be effective, and would undoubtedly cause us to be perceived by the rest of the world as more of a threat than they already do.
Saddam is a genocidal war criminal but is there a reason he can no longer be "contained"?
If he gets nuclear weapons that would certainly be a reason.
The Bush Administration says that Iraq must disarm themselves of WMDs as they agreed to do, and that they must demonstrate that they have done so. Meanwhile Blix says that Iraq is not "actively cooperating" with the inspectors, so the outlook is not promising.