@bloonewbIt's a bastard child of that which you speak of, and England in the 1100s-1500s.
Take a look at the Angvin Kings, and the War of the Roses. It is close to the HRE, but every individual part of Westeros has a geographic relation to England, and wider France. The North, is the North (of England), the Reach, quite a lot like the South-West of the UK and Aquitaine. The Kings of that day barely kept their Dukes under control, and it was pretty fucking vile. It's funny- a lot of Shakespeare's most boring plays are now rivals to GoT, via some of the BBC's dramas I think (complete with lots of fucking, per GoT). It has a lot of Germanic features to the realm, but I think a more Anglo-Angvin approach to politics, peoples, places and culture.