I strongly disagree with this multiple parts of Martin's world have fairly obvious connections to ours, however loose. And I think he's said that most of the foundation story was inspired by the Wars of the Roses, which, as a pretty voracious reader of European history, I can plainly see. I don't think this makes him a weak or lazy or bad writer. I just disagree with you that none of the places in the novels seem to have historical equivalents.
For me it's a yes and no. I can see clear parallels where ideas could have begun, but I think GRRM mixed and matched to create new places as well. For example I can see a lot of Spain in Dorne, but I live here and there are many things that are blatantly NOT Spanish.
There is only a very small area of Spain that can be considered desert and its not even very sandy.
Though a lot of people share this misconception, they have virtually no spicy foods here.
Some people have mentioned a time period when women had more rights in Spain and that may be true, but Dorne has been carrying that torch for a lot longer.
I think the idea is that there was a lot of inspiration from real places and peoples, but also a lot of play was allowed to make them unique.
To resume, its not as simple as just saying the Reach is France, or Dorne is Spain, but you can outline the parallels that they do share. The Iron Islanders share a seafaring and sea conquering nature with the Vikings, but I don't see many cultural parallels beyond that. They have different religions, different traditions, different societal hierarchies, that stop me from making simple comparisons that equate the two.