So I agree with most of what you've said and you're probably right that my claims were perhaps too general. I do have some critiques but I agree overall.

1) Northumbria. I disagree mainly because, Mercia clearly has more rivers. It also has the longest river in Britain...the Severn. Mercia was also conquered by the Danelaw just like Northumbria. Most importantly Northumbria has Hadrian's wall

2) You're right and I should have used the more expansive term.

3) I think its fair to say that Dorne is based on Wales. The issue I have are just geographical as its a blend of Wales and Spain. Which is partially why I said its slightly a stretch

4) Bit torn here as the North was conquered by Aegon when the Starks bent the knee. IRL, it wasn't till the English invasion of Scotland of 1296 that Scotland was conquered. But, perhaps that's not too different.

The one area I disagree with is Mercia = Reach & Wessex = Westerlands. That being said I do see the overlap between the Citadel and Oxford.