Final answer:
The factors that convinced Americans of Tet's defeat were the TV coverage of the war's cruelty and the revelation of the My Lai massacre. These were genuine concerns and eroded public trust in the US government.
Step-by-step explanation:
Several factors mentioned in the clip may have convinced some Americans that Tet was a defeat for the US and South Vietnamese forces. One factor was the television coverage that showed the carnage and cruelty committed by South Vietnamese leaders. Another factor was the revelation that US troops had massacred unarmed civilians in the village of My Lai.
These factors were genuine concerns for many Americans because they raised doubts about the progress and honesty of the US military and government. The graphic images and stories eroded public trust and led to a growing opposition to the war.