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Austria acquired Serbia and Oltenia in 1718 however lost them again in 1739. I dont think this loss is too hard to avoid, lets say the war ends a draw without territorial exchange. I think this can be reached by making the Austrian leadership less horrible.
I just read in Michael Hochedlinger's Austria's Wars of Emergence, 1763-1797 that the Austrian plan with the territories was settlement with german catholics like in the Banat. This was less successfull than there but it still happened.
So what are the effect? IMO in short term the war doesnt devastate the Banat so even more germans there which would be a pretty strong presence (was already OTL). The military frontier would be south of the Danube. This would avoid a lot of the tension between the hungarian nobility and the dinasty - not reintegrating this territories into Hungary was one of the main reason of resentment. Also this butterflies the fleeing of a few hundred thousend serbs into Hungary.
The territories are not significant enough themselfs to influence the other wars of the 18th century and honestly I dont think they strengthen Austria in this time period to be significant.
The interesting question would be how things develop in the 19th century. We have a Serbian Kingdom under Austrian rule for a century with significant german populace and I would think much better developed than OTL. Also the whole or nearly the whole of it is part of the military frontier. Austrian Wallachia or Oltenia is the same except that the other part is only an Ottoman vassal instead of direct control.
How would the national movements look in the 19th century? How is Vienna viewed by the serbs and romanians? In one hand they were freed from the Ottomans by the Habsburg. In the other hand attempts to catholisation, german settlement and much more efficient Austrian administration (and taxation) may not endear the state to the locals.