You could be right in your analysis about the actual centripetal and centrigugal forces in Spain, as Spain is divided in different regions with also different languages, which tend to struggle for independence, especially the Basks, while other regions, as for instance Cataluna, is opting for more self-government.
We have that problem even stronger in Belgium, with 3 different people and 3 different languages, and the only centrifugal force is the actual king of Belgium.

But I don't think this centripetal forces didn't exist that way in Napoleonic Spain, as the nationalistic feelings of the Spanish population were quite strong, remembering their rich history and the proudness of the Spanish themselves
(my direct family who lived in Grenada for more than 30 years - from the end of the fifties till 1992 - is still testimony this statement when remembering their stay - they came back to Belgium for health reasons - they owned a magnificent land-house facing the Generallife), but also in view of the War of the Spanish Succession and the Spanish crown being taken by Philip V., a Bourbon and relative of the French king..

To learn more about the history of the Spanish Netherlands, I would suggest a visit to the websites given below :

http://www.theotherside.co.uk/tm-heritage/background/flanders.htm
http://www.historylearningsite.co.uk/revolt_of_spanish_netherlands.htm
http://www.zum.de/whkmla/region/lowcountries/spanneth.html
http://www.encyclopedia.com/doc/1E1-NethAusSp.html

Cheers and best wishes

Marc