Have whomever is in the white house and foggy bottom not be so convinced of a need to save france's bacon. Instead have them reach out to Ho and do a deal - "We'll guarantee your unity and independence, offer you trade, and protection from China. In return, you offer us basing rights, tell Russia to get lost, and tone down the whole comintern shebang"
It would need Ho to be in the right mood, and there would need to be some personnel changes in the vietnamese high command(s) (N & S). I think the first is very possible, I think the later is the real tricky part.
French/US clients in the south would scream bloody murder, as would no few French. Of course in OTL we ended up supporting at least 1 coup in the south, and it's not like the US and France have the long deep and abiding mutual admiration - regular allies of convenience is different than kindred spirits - so I'm not sure those are dealbreakers.