We would still lose because the US military (from 1946 the mid-1950s) was fully invested initially after WW2 to demobilization and then fully invested in the Korean War at that time. Additionally, our government was trying to support the rebuilding of Western Europe. We had no time nor the inclination to do much else than the support we did have for the French.
The better question would be, what would happen if the US used their political will to support Ho Chi Minh and force the French to pull back from Indochina. The French thought they were doing well through 1947 until French General Valluy failed. He could have negotiated at the height of the issue (using USA as an intermediary) but instead like all great powers who used colonization they lost.
In order for the US to help the negotiations, it would have to happen before the catastrophe's on RC4 and the loss of Nationalist China...after the PLA won, they then turned South to support Ho Chi Minh and that support in separately linked China and Viet Nam to the Western World. This link caused the misconception of the Western World that it was one big domino effect of Communism rather than a nationalist struggle.