It will be impossible for China to have nukes during the 1950-1953 era, as the country which was recovering from the Japanese invasion, was hit by the civil war. At that time, not many countries were willing to recognise the PRC due to American pressure. Britain and France were two of the few non-communist European countries that recognised the PRC but that is more of due to a surge of socialism in both countries than tolerance. So China will not have the funds to own nukes, and even if they do, Mao can't do it since he ran on a "help the poor" platform. Nuclear weapons were considered extravagance.
The Soviet Union will not have reacted strongly despite having close ties with PRC at that time, as the US Army was considered the strongest in the world, riding on its victories against Nazi Germany and Imperial Japan. The Soviets had already lost 20 millions to WWII itself, I do not think they have the manpower and skills to spearhead an effective army against the US.
Hence, I say the communists got lucky, cause Uncle Sam practised restraint against them. I think everybody knows that when Uncle Sam (and the American public) wants a country pulverized, he can get it pulverized and make it look legal.