It was 1948, so not nearly enough nukes to irradiate the planet. We'd lose several major European and Soviet cities, tops, maybe a few important US military bases in Europe.
After that, however, it was going to be an ugly war. Germany would be the primary battleground, especially so close after the end of WW2 and the near complete annihilation of its industrial capacities and infrastructure. Quite simply, when the war's over, it'll be a miracle if there's a Germany intact.
Allied victory is more likely, but not a given, especially with superior Soviet numbers and better tank tactics, and the memory of what the Nazis did in WW2 will drive the Soviets to prevent a war in their territory at any cost. It might end in a truce, but it would be an especially bloody and ruinous truce. A victory would be only slightly better, if not worse. America would be bloodied, Europe ruined, the USSR in shambles. China's ascension to world power is sped up on account of everyone else having a hard time in the 1950s, but that's dependent on Mao not being an idiot.