about SPAIN and SPAINS

About "Spain" and "Spains".
"Spain, or "the Spains", referring to Spanish territories across different continents in this period, initially covered the entire Iberian peninsula, including the crowns of Castile, Aragon and from 1580 Portugal."
"Habsburg Spain is a contemporary historiographical term referring to the huge extent of territories (including modern-day Spain, a piece of south-eastern France, eventually Portugal and many other lands outside the Iberian Peninsula) ruled between the 16th and the 18th centuries (1516–1700) by kings from the Spanish branch of the House of Habsburg (also associated with its role in the history of Central and Eastern Europe). Habsburg Spain was a composite monarchy and a personal union."
"A composite monarchy (or composite state) is a historical category, introduced by H. G. Koenigsberger in 1975 and popularised by Sir John H. Elliott, that describes early modern states consisting of several countries under one ruler, sometimes designated as a personal union, who governs his territories as if they were separate kingdoms, in accordance with local traditions and legal structures. The composite state became the most common type of state in the early modern era in Europe. Koenigsberger divides composite states into two classes: those, like the Spanish Empire, that consisted of countries separated by either other states or by the sea, and those, like Poland–Lithuania, that were contiguous."
"A personal union is the combination of two or more states that have the same monarch while their boundaries, laws, and interests remain distinc."
"The Iberian Union was the dynastic union of the Crowns of Castile and Aragon and the Kingdom of Portugal that existed between 1580 and 1640 and brought the entire Iberian Peninsula, as well as Portuguese and Spanish overseas possessions, under the Spanish Habsburg monarchs Philip II, Philip III, and Philip IV. ... This was a personal union, so the Kingdoms of Portugal and Spain remained independent states, sharing only a single monarch." "The term Iberian union is a creation of modern historians."
"The 1812 constitution adopts the name As Españas for the new nation. The 1876 constitution adopted the name España (Spain) for the first time."
"La denominación "reyes de España" empieza a darse informalmente a los Reyes Católicos y se hace común con los reyes de la casa de Austria, aunque sin ningún valor político ni jurídico, pues solo hacía referencia al concepto geográfico heredado de la Hispania romana."