The POD is that the Ottomans break the first siege of Vienna in 1529, particularly by lot better weather occurring than in OTL.
The way I see it, The Ottomans would control Vienna for maybe a decade if that. Then the Holy Roman Empire reconquers it. However in the longer run the Ottomans would rule over what became the Hapsburg realm of Royal Hungary. One major effect of this would be that in this TL Hungary would became a majority Protestant country.