RousseauX
Donor
If the US had understood Mao was not an "agrarian reformer" and was an dedicated opponent of the West and the US, it would have acted much more different. Instead of trying to mediate a peace deal between Chiang and Mao, it would have given Chiang the military and economic aid he needed to win the war. It would have been cheaper than having to support Taiwan, and fight wars in Korea and Vietnam.
Completely wiping out the CCP in a few years was impossible given that Chiang could not have isolated the CCP from the Soviet Union. However, I think it is possible that Chiang could have driven the CCP from Harbin and consolidated control of southern Manchuria's important industrial base.
US troops would not be needed, but US advisers at the unit level plus a commitment to arm and train troops to put most of Chiang's army at the level of the US trained divisions in X Force would have enabled Chiang to keep control of the country.
Chiang likely only needed to make a few reforms up front that would have helped him greatly - centralize the military payroll, enact compensated land reform, and start an anti-corruption drive. If he did that, the US would only need to make sure enough money flowed so that Chiang did not hyperinflate his currency, and Chiang would have won the civil war.
So in effect, how is this really all that different from Vietnam?