I repeat, everything is politic, believe me
. Spanish team hasn't played at Bilbao for example because it's very dangeous due to the radicals around there (I don't mean ALL the people, but there are a lot of political radicals and the Spanish team playing there would be a motive to do a lot of bad things and not for football. (politic again: ETA,HB etc, etc)
In Barcelona, well I don't think Maragall (the president os Catalonia) see this with good eyes (politic again). And you say Sanchez Pizjuan? In Andalucia Spanish team has been always supported A LOT. And why do you take Andalucia or Galicia inside the independentist? It's just Catalonia and Basque country.
And yes, Valencia and Madrid are always the main supporters for the National Team.
But I repeat, I don't think this is the main problem for Spanish Team.
Italy for example at the beginnig of the world cup was very separated in feeling about the national team due the scandal of the Juve, Milan, etc, etc...But what now? I'm sure everybody says: "Forza Italia"...I mean that, football people like us beleive in cups and goals, not in politics.
PS: I was at Firenze for 5 days on August. Your city is WONDERFUL