I think General Finlay had a timeline called "Outrun My Gun" about a McArthur Presidency which used nukes on china.
I'm not sure I'd have taken such a sanguine view as to the use of nuclear weapons in the Korean war. That kind of crap definitely comes around, and payback's a bitch.
A USSR confronted with an America ready to use Nukes on its doorstep? The Soviets really had no faith in the integrity of the United States. I there's a good chance that things might have escalated then and there. Alternately, an even more paranoid and defensive Soviet Union would have been more desperate to even the odds, and would have been more willing to give credence to Americans initiating a war.... which would have made them much more willing to do a first strike. World War III within 20 or 25 years at the outset. There were a number of potential flashpoints - the Berlin Blockade, Cuba, etc. which could have gone hot, and the altered history would likely have contributed additional flashpoints.
A China which had had nuclear weapons deployed against it.... Well, its unlikely that the Chinese government would have been overthrown. But its much more likely that either the Chinese would draw closer to the Soviets for their nuclear umbrella, rather than breaking away in the subsequent decade... or they would have been far, far, far more aggressive in pursuing and developing a credible nuclear deterrent earlier and much more willing to use it.