the Hapsburg Empire was under attack from Prussian backed revolutionaries. Reichenbach put an end to that and created the basis of the first coalition and the first revolutionary war.
If you can get them to not have a convention (Austria and Prussia) the odds are they'll end up at war with each other, with a revolutionary France aligned with Prussia (at least at first, that's kind of what the convention was about), and then the devolved republics of the Hapsburg empire could make for a confederation and buffer to both the Ottoman and Russian Empires. I doubt Prussia would turn on France in such a scenario but maybe we see a coalition of Russia, Prussia, Britain and Spain?
Against France and the devolved republics? That would still be a powerful coalition like OTL sending republican France and the devolved republics into internal chaos and violence as the republicans would try any means necessary to preserve their republics like OTL with the Reign of Terror. Hence, a unstablized republican France and devolved republics would occur like OTL with the result that a strongman like Napoleon would have been needed to defend the republics against the coaliton, and spread Revolutionary ideals throughout Europe like OTL.
I can see why a revolutionary Prussia could turn against France in order to get its hands on the devolved republics but why would the coalition powers allow a Revolutionary Prussia to join them? They were against the ideals of Revolution and republicanism.
Europe really was not ready for Revolutionary ideals and republicanism without violence. For a peaceful transition to Revolutionary ideals and republicanism throughout 18th century Europe, more time is needed for the middle class and bourgeoisie to grow enough in numbers and influence and for literacy levels and schooling to rise to cover the whole populace in order for them to read about and accept the Enlightenment. However, that is assuming that the populace get out of their innate tendency to reject change and assuming that the reactionary monarchies and nobles don't stamp out and ban Enlightenment ideals in their territories because these ideals would rightly be seen as a threat to their power and privileges. Constitutional monarchies would have been a good solution for change and for a peaceful Europe to happen.
Otherwise, the only way for Revolutionary ideals to spread throughout 18th Europe is by force of arms. If Napoleon had been more ruthless in dealing with Austria and Prussia such as actually deposing their respective monarchies and encouraging the respective peoples to form their own governments, Revolutionary ideals would have spread more thoroughly. Russia would still be resistant, though, because of the low levels of literacy and high superstition among the Russian populace. If Europe had minded their own business OTL, there would have been a good chance that Revolutionary France would have imploded because of divisions between them, royalists, and catholics. Thank goodness Europe went on and intervened OTL.