The US was largely responsible for Dien Bien Phu itself. After WWII France had no interest in fighting the Viet Minh, and we told them we needed them to do so to contain communism. We funded them and armed them to the teeth; if you see French soldiers in Dien Bien Phu they look like US GIs from 1945 (same gear, helmets, etc.). In a grim foreshadowing of the Bay of Pigs a few years later, promised US air support simply never came.
Uh, no. The US flew almost 700 sorties in support of the French at Dien Bien Phu, but as Ike had already disavowed any intent to get involved, the operation was done covertly. Two US pilots lost their lives.
https://en.wikipedia.org/wiki/Battle_of_Dien_Bien_Phu#American_participation
Ho Chi Minh, his general Giap, and all the rest of his fellow commies were responsible for what happened at Dien Bien Phu. Until Giap opened up on the French positions with superior firepower from higher ground, no one in France or the US had any idea about Viet Minh capability. The French had picked the location in order to cut Viet Minh supply lines.
After WWII, the French had insisted on the return of all of their prewar colonial territory, and DeGaulle took a hard line against the countries that had just liberated France, refusing to join NATO, etc. The US didn’t give a crap about Indochina, it only wanted to keep France in the fold.
Total waste of time that was, too, since the result of French mistakes at Dien Bien Phu was to see the hung over French public turn 93% against trying to hang on to Indochina, and the fever pitch against the US and UK get even worse. It’s still a factor in French elections, even among the best-of-the-worst politicians and political parties.
During WWII, Joe Stilwell suggested supporting Mao instead of CKS, an attitude probably influenced by the rocky relationship between Stilwell and CKS, and the great public relations the Maoists had when they received him as a visitor. He didn’t want the US to switch sides, merely support both in their fight against the Japanese. CKS also ran and supplied the Vietnamese resistance to the Japanese occupation.
Truman refuse to give US support for Ho Chi Minh’s takeover. That’ll learn Ho.