I have read endless memoirs, papers, and books on the subject. The lessons of WWII were not applied in either Korea or Vietnam. Yes..both presidents (LBJ/RMN) were fearful of a wider confrontation during Vietnam. Politics doesn't mix well with warfare (lesson #1). But isn't it the ultimate irony that we were concerned about a wider conflict while we were simultaneously building 1,000's of nukes and militarizing europe? Unfortunately, we didn't utilize our military power early in the war with Vietnam or accept their early offer to discuss peace. Had we done either or both, I doubt the war would've lasted through LBJ's term.
I agree that Iraq is a no win situation. You are more "courteous" or perhaps diplomatic than I on Iraq. We should have given your ultimatum about 2 years ago.