The best answer is probably “partially”.
There are very clear elements from (particularly) English history throughout the A Song of Ice and Fire series.
The biggest single source of characters and event is probably the War of the Roses, but there are loads of others (some of them I mentioned in another answer).
And yes, the concept of there being “Seven Kingdoms” is probably borrowed from the Anglo-Saxon Heptarchy.
Just like other fantasy authors, however, George R.
Martin’s interest isn’t in creating a simple facsimilie of medieval England or any other country; he has thrown a lot of different historical elements together and sometimes added creative twists of his own in the interests of creating compelling and interesting narratives.
So it’s not accurate to say bluntly that “Westeros is GRRM’s version of England” or any other country, but it is fair to say that the A Song of Ice and Fire novels and thus the TV series are heavily influenced by the history and culture of medieval England (and the fictional portrayals of it as well).
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