Bourbon Austria before 1800.

WI the Bourbons inherited the lands of the Hapsburgs, lets say like OTL the male line of Hapsburg dies out with the female line married to the Bourbons.

How would that effect Europe.
 
With quite a similar impact to when the Bourbons got the inheritance of the Spanish Habsburgs.
Two things are almost certain :
- the same person will not have both crowns on his head or will not retain it long (for example if Louis XV of France had married Maria Theresa). Sure, the 2 Bourbons heads of the 2 kingdoms/States will try to build some kind of strategic alliance … which will be fledgling because the 2 kingdoms/States had obvious different and sometimes divergent interests.
- you will have a war of Austrian succession because such a union is nothing less than the new avatar of Charlemagne’s empire.

What all these successions showed, from 1700 on, is that dynastic diplomacy was less and less efficient in modern ages that were the ages of emerging national/imperialist diplomacy.

Sharing the same king with Hanover was more a liability than an asset for the government of Great Britain.
Having another Bourbon on the Spanish throne was an obstacle from French expansion. Concluding a strategic alliance with Austria without beforehand having settled the matter of the Austrian Low Countries that were whose acquisition had been and remained France’s long term goal was more a problem than a solution for France.
The fact that William II of Germany and Nicolas II of Russia were cousins did not prevent their countries going into world war 1.

One thing almost certain is that you will have a war of Austrian succession.
 
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