First of all, there's a funny thing in the map someone posted a page ago: it supposedly was a Reconquista Map, showing battles connected to the Reconquista. The problem is that the Battle of ALjubarrota, displayed in Portugal, had little or nothing to do with the Reconquista - it was fought between the Portuguese and the Castillian-Leonese, with no Arab intervention at all.
In regards to the "Kingdom of Spain": I quite like the idea, but as someone else said, it would have been impossible for Iberia to be united under one single political entity during most of the CK timeframe. But one thing we do have to account: for long, the name "Spain" meant the same as "Iberia". If you went and asked a 13th century Portuguese if he considered himself Spanish, he would answer positively. Portuguese, Castillians, Leonese and Aragonese all considered themselves Spanish. The problem was when the Kingdom of Castille-León, united with the Crown of Aragon, "stole" the name. But as someone pointed out, Philip II was the first monarch to use the title of King of Spain - and that was after he inherited the Crown of Portugal.
Summarising: during the CK timeframe, "Spain" is to be interepreted as a synonym for Iberia, and may not refer to any political entity (like it does nowadays) but rather to a geographical area.
