Nineteen people with boxcutters took out a chunk of an American city. A smaller group with biologicals or chemicals could do a lot worse.

You are right that we're not dealing with WWII tactics any more. We don't have the luxury of seeing our enemies lined up on borders like a "Risk" game. It no longer requires governments, air forces, armies, or missile silos to do major damage, and we can't easily see the enemy coming.

Afghanistan and Iraq were threats to world peace. For that matter, so are North Korea and Iran, and they will have to be dealt with sooner or later, diplomatically or otherwise. Saudi Arabia needs to clean wahabbism out of its system, and I don't see how that can be done easily. Our forces are dealing with terrorists in Africa, although this gets little press, probably because they don't want it to get any press. Libya is cooperating in disarming now, and its cooperation broke up the Pakistan nuke ring, an accomplishment that was probably worth the price of Iraq all by itself. Although I understand the Official Story now is that Libya cooperated solely because of the brilliant negotiating skills of Britain.

Incidentally, a nation does not have to threaten the American homeland specifically to be a threat to world peace.

BTW, this "they were never really a threat at all" gambit has been tried by the Left in connection with the Soviet Union, but when the U.S.S.R. broke up and the former Soviet military people started talking, this approach faded out pretty quickly.