The original question had to be edited. I would say that the March 1968 reevaluation of the Vietnam War was largely driven to satisfy growing domestic concerns as opposed to international ones. When Clark Clifford advises the President about the state of the conflict, he does so with domestic discord in mind:
I was more conscious each day of domestic unrest in our own country...Draft-card burnings, marches in the streets, problems on school campuses, bitterness and divisiveness [angry disagreement between groups] were rampant.
The optimism with which President Johnson had been able to commission the start of the war in his discussions with the American people was replaced by cynicism and a stunning lack of faith in government. With each day in Vietnam, the narrative was that either the government was incompetent to not know what was happening or that the government was deliberately lying to the American people. Both are driven by domestic reality. The mood in the country, especially after the bloodmath of the Tet Offensive, was that the war was not as winnable as the public was led to believe.
President Johnson and his advisors had no choice but to examine the war in domestic terms. Given the mounting public dissatisfaction with the war, the international arguments were no longer proving to be compelling. The "six o'clock news" each night was telecasting more despair regarding the death count in the war and Americans became more horrified with the amount of dead and wounded who were returning. The war had begun to enter a realm in which public legitimacy of the government was waning. The reevaluation of the war in 1968 was carried out with domestic concerns in mind. The large amount of public outcry led to this. The war was complex and intricate, with victory being defined in different and more nuanced metrics than previous conflicts. This led to a reexamination of the war effort with domestic concerns at the forefront. Being able to communicate these nuanced positions became increasingly unlikely primarily because public opposition was so vociferous. It is here where the reexamination of the war was more driven by domestic concerns than anything international in March of 1968.