what if macarthyr was not removed from his post?

I don't either.
The fact that the US supported Ho in WW2 was only due to the fact that he was figthing the japanese.
The US also supported Stalin in WW2, which did not prevent the Soviet Union of becoming a foe after WW2.

Ho had helped create the french communist party, had lived for some years in Moscow in the 20's and 30's, and later with help of the soviet secret service founded the vietnamese communist party.

Altough some people have a somewhat romanticised view about him, Ho was in fact a die hard communist, and for me there can be no doubt on which side he would have been(and actually was) in the cold war.

And, altough the US "oficially" supported France, in fact they were already looking for anti-communist vietnamese elements in the colonial army which could take over the country after France would have left.