Your challenge, if you choose to accept it, is to prevent the Habsburg domination of Europe which occured in OTL. Cut them short, kill them off, stop them from even beginning to gain a foothold. It's quite a tricky one to pull off plausibly. They don't seem to be that much of a threat early on, and ripping one of them out early on normally merely diverts the flow down a different branch of the family tree. Leave it too long, however, and - bam! - suddenly there are hoards of the blighters. You'll have to be cunning...
Best of luck.
Best of luck.