If you are asking if I think more troops will be required to take firmer control of Iraq...I suspect this could end up being the case...but if it is the case it should be a massive build up of troops. If we start piece mealing troops into Iraq then the comparison to Vietnam will become pronounced.
In Vietnam there was a well organized Guerilla force in place before we ever entered the fray and in addition there were well organized NVA forces to contend with. Both of these forces had decades of combat experience prior to the US entering the fray.
Even then...US forces beat them at every turn of the game...and if the conflict had not been micro managed by cilvilians...piece mealing troops into Vietnam...controlling targets...strategic and tactical...the conflict would not have been prolonged and an ultimate withdrawal of our forces would not have happened.
Generally, when things go wrong with the military operations, it is because of civilian micro management.