You left out
1. Backing an unpopular Government. Think of the US backing Saddam in a civil war. The South Vietnamese regular army and the civilian militia had no real motivation to fight. The officers were often corrupt and only out there to make money from the war. From the top down the tactic of the South Vietnamese government was to rely on the US to win the war for them.
2. Use of innapropriate military tactics, that is, relying massive superiority in fire power. This worked for set piece battles only, so the Vietnamese did everthing they could to avoid them. If they couldn't, they tried to fight in close, where massive air and artillery support would not help.
3. No real respect for the Vietnamese people. The massive rise of red light districts, drug use, corruption and perception of the Vietnamese as 'gooks' says it all.
There was no failure to take the fight up to the enemy. Ia Drang was a good example of this. The Vietnamese, however, learned quickly that they could not fight against superior firepower head on, so they did all they could to avoid this.
The draft was an issue. However, many soldiers appear to have tried to do their duty. They would have realised soon enough, when they got there, that they 'enemy' was not going to stand out there and fight them like the Germans. The enemy could be everyone from the woman working in the rice paddy to the old man riding a bike.
The amount of money spent on the war was fantastic. If money and weapons alone could have bought victory, the US would have won hands down.
The communist fighting force was definitely better motivated. They were fighting for their country.
The Vietnamisation plan had to be put in place. If the South Vietnamese would not fight, and did not support the war, then what was the point of it?
The anti-war movement only stated the obvious. In vietnam itself, there was a still massive army fighting, with all the weapons it asked for.
American soldiers, on the whole, I believe, did as they were ordered. They certainly killed many Vietnamese soldiers. If that was all that was required to win, then the US would have won easily.
The Government backed the war with massive amounts of men, weapons and supplies. The people of Vietnam still fought back.