Plup, plup, plup....that's the sound of the shit hitting the fan, and this fan is industrial-size. Anus-clenching situation throughout the Far East. Korea, Japan, maybe Taiwan, Alaska, and the US West Coast are in for fallout from all the nuclear strikes.
Outside the nuked cities, which tended to be in the more heavily populated eastern portion of China, the Soviet nuclear bombardment has also played havoc with Chinese agriculture. Nearly all the best Chinese farmland is in the east. Some places get two crops of rice a year. Lots of destruction and fallout, right during planting season. Expect famine among the surviving Chinese. The USSR's main agricultural areas weren't touched, and all fallout is heading east, towards the Pacific.
I would also think the North Vietnamese are up the creek. China can no longer support them. The USSR will have enough to do in other places. Maybe the North Vietnamese agree to a negotiated peace. Smartest thing to do before the Allies defeat them, now that support isn't likely to come for a long time, if ever.