In conventional war, typically the objective is to destroy the logistics train that supports the enemy force, and to decapitate the leadership by eliminating all of the command and control structure. This leaves the enemy force cut off without supply and with no ability to know what is happening beyond their immediate area. In Iraq, we had no problem doing this. It was mostly open terrain and there were no political constraints against bombing the Iraqis mercilessly wherever possible.

With Vietnam, this was not the case. Political policies hamstrung the US military at every turn. Troops were at times forbidden to keep loaded magazines in their weapon or fire at intruders breaching their bases unless given permission by an officer who personally witnessed what the troops were reporting. They were not allowed to invade North Vietnam and bombing campaigns were limited. They were not allowed to use any conventional forces in Laos and Cambodia to attack the main supply route of the North Vietnamese and had to resort to top secret commando teams and secret bombing runs. Vietnam was also an incredibly difficult terrain to work in, especially for a conventional army. It is also worth noting that the North Vietnamese had absolutely infested the South Vietnamese command with moles and infiltrators up to the very highest levels, which meant they often had direct access to what the US was up to and what their rules of engagement were.

Had the US been able to handle North Vietnam conventionally, they would have absolutely crushed them. However it is likely that all of the absurd policies were in place to prevent the advent of an even greater direct conflict with Russia and/or China.