Following FDR's death in April, 1945, how did America's position on Indochina (Vietnam) change when Truman took office?

It is really remarkable how quickly foreign policy changes in reaction to a change of presidents. During World War II, the United States had earned a good deal of favorable public support in Vietnam for confronting and defeating the Japanese. Franklin D. Roosevelt had an international reputation for being opposed to colonialism, which was widely heralded in Vietnam to dissuade foreign powers (in particular to the French) from interfering in the internal affairs of Vietnam.
Ho Chi Minh, a communist as well as the de facto leader, even went so far as to quote from the Declaration of Independence in a speech on the day Japan surrendered. The speech was interpreted by the international community as an attempt to dissuade Allies from intruding on the sovereign power of Vietnam. Ho Chi Minh was a pragmatist. During World War II he assisted American soldiers and provided intelligence to the CIA against the Japanese. He hoped to bring American foreign policy to support his side and prevent further intrusion in the politics of Vietnam. Unfortunately, this amiable relationship with the United States was short-lived.
Truman held a very different worldview than that of his predecessor. Truman and the presidents that followed him (up through President Nixon) saw the fight to stop the spread of Communism as one of paramount importance to the United States and the Allies. Historical evidence suggests that Truman and the presidents that followed were privately hesitant to ratchet up efforts to thwart the spread of Communism by entering into a prolonged conflict in Vietnam.
Though these may have been private thoughts, publicly and as a matter of policy, Truman and his successors chose conflict over truce, leading to a prolonged engagement that costed billions of dollars and the lives of many Vietnamese and American soldiers.
https://alphahistory.com/vietnamwar/harry-s-truman/

https://www.docsteach.org/documents/document/ho-chi-minh-truman

https://www.history.com/news/us-presidents-vietnam-war-escalation