I really would doubt that if the US intervened in China in 1947 that the US would lose badly. The Communist Chinese forces were armed with a mixture of captured Japanese and US weapons (taken from the Nationalist) plus a trickle of soviet arms.
In 1947 the Reds lacked any industrial base capable of producing weapons. US intervention would probably have prevented a lot of the disasters that led to the collapse of the Nationalist forces. it would have also boosted the morale of the Nationalist and likely lead to Soviet withdrawal of any support for Mao. It needs to be repeated that Stalin did not like or trust Mao.
The Nationalists already had a 4 to 1 advantage over the Reds in manpower alone. Including their armaments, logistics, and foreign aid, their advantage *should* have been enough to swat the commies like flies. What destroyed the Nationalists was top-to-bottom corruption: generals didn't report the deaths of footsoldiers in order to pocket their salaries, ammo and food being pilfered and sold to the Commies, footsoldiers being paid in increasingly worthless banknotes, etc.
It got to the point that by the time the Commies were approaching the Yangtze River, KMT footsoldiers were being paid in silver coins which they stuffed in their pockets. As a result, they couldn't outrun the advancing Commies and were sitting targets. Entire KMT units defected without firing a shot. Finally, it needs to be noted that the Commies attracted countless recruits through promises of land reform. The KMT will recruit based on...what? Even a well-paid mercenary army can't be relied upon to fight their fellow countrymen.
Active US involvement would have further demoralized the KMT rank and file. It would have been a reverse of Vietnamization, where instead of the Americans withdrawing and the South Vietnamese entering the fight, it would be the Nationalist Chinese defecting/collapsing and the Americans entering the fight. Obviously this doesn't end well.