Different battles play out leading to the U.S. capturing half of it - they split it with the USSR into a Western Zczech Republic and Eastern Slovakia. (Say, no Battle of the Bulge, some German slips-ups before on the wEstern Front, maybe some luck keeping the Soviets delayed a few weeks in moving West.)
That part, I think is somewhat easy, at least compared to the other. Although...is there a way that, instead of a Czech Republic/Slovakia split, the USSR agrees to let it stay neutral and Finlandize it?
Maybe; let's say that there is *huge* desire for the Czechs to join NATO. Would the Soviets, seeing a way to keep them from getting into NATO (because that would mean another area East Germany would have to guard against), be willing to give up their part of Slovakia in order to keep the peace?
Maybe... let's say that before NATO forms, in 1948, the Berlin Airlift sees a lot of flights come from the south. The Soviets would have to be willing to bend to negative publicity, but if there are protests in Slovakia against the split, and they see a way to cut off the WEst from that route into East Germany, they might decide, as a result of the airlift, to settle the dispute in part by agreeing to unify the countgry in return for it becoming non-aligned.