This reevaluation was conducted mainly for domestic reasons, not for international ones.
If the US had been mostly concerned about its international standing at this point, it might well have simply continued with the war. The same fears that had previously existed about things like the domino theory and American credibility still applied. But the war was no longer popular at home. The Tet Offensive, in particular, had eroded American support for the war. Americans no longer believed that the war could be won. They no longer trusted the Johnson administration to conduct it. This was the main reason why President Johnson reevaluated the war and chose not to run for reelection. He was concerned with the impact of the war on domestic politics and on the chances for the Democratic Party in the upcoming elections.