Today, The Duchess of Devonshire's Gossip Guide to the 18th Century posted on the differences between the political map today and in the 18th Century, explaining why German royal consorts were never the princess of Germany among other things in the post "What a Mess." Including a great link to a historical atlas that shows European political boundaries at the turns of the first to the twenty-first centuries, there have been some changes.
To tie this in to Jane Austen a little more, I will note that those German royal consorts included:
Caroline of Ansbach, wife of George II and mother to George III
Charlotte of Mecklenburg-Strelitz, wife of George III and mother to George IV and William IV
Caroline of Brunswick-Wolfenbüttel, wife of George IV and mother to Princess Charlotte (who would have been Queen Charlotte had she not predeceased her father and grandfather)
Leopold of Saxe-Coburg-Saalfied, husband of Princess Charlotte
Adelaide of Saxe-Meiningen, wife of William IV
Victoria of Saxe-Coburg-Saalfeld, mother of Queen Victoria
Albert of Saxe-Coburg and Gotha, husband of Queen Victoria
It went the other way as well, many of the non-throne-inheriting English royal children also married Germans.