Ho Chi Menh went to the USA and worked in Boston and NYC during the 1910s. During that time there was a large piece of the population in USA that were anti-imperialist remembering how we got rid of the British. He admired us. After WW2 he connected with the OSS and was actually helped back to health from an American medic. He sent a letter asking for help against France to Pres. Truman, which was planning a coup to take back Vietnam. It was never answered and Ho continued on his path with a communist Vietnam. No one knows what difference our help would have made to Ho as by then he was a pretty committed communist. But after WW2 the hard line anti-communist had taken control of the US government and there was no way we would help Ho.
I don't think Chiang Kai Shek could have beaten the Communist forces even if we helped him. The civil war had been put aside to help defeat the Japanese, but after that the war continued between the two. The USA actually tried to broker a peace but failed. Our experienced diplomats in China knew that the Communist had the upper hand and would win, advising our government to build a constructive relationship with the CCP. However, the ambassador, who had no experience in China had the opposite view and it was that view the anti-communists who controlled most of Washington DC went with. It didn't take long before Mao broke the deal the Americans had brokered between the two and the Communist drove Chiang to Taiwan.
FYI- As a child in the mid 1960s I lived in Taiwan. My father, in the Air Force, was in charge of the final delivery of F5s and F5a's to Chiangs military. My parents had lots of connections with him and Madam Chiang would come to our house just to talk with me (she loved male children). She was in her late 60s during that time, while her husband was pushing 80. I met Chiang Kai Shek once when I was 7 and I remember he was grandfatherly to me. Madam Chiang was educated in the west and was comfortable with western culture. She would come to our house for "Tea" with my British born mother.