I think there's something lost in translation here, because Catalonia is not a "county" in the sense that, say, Norfolk is a county in Massachussets, but an autonomous community. Autonomous communities, legally speaking, would be closer to Scotland in the UK . How many competences of the central goverment have been devolved exactly varies from region to region, though.
Puigdemont's party's immediate purpose was to get greater self-goverment for Catalonia (eg: more devolved authority) rather than full blown independence. The central goverment's stonewall of the former led to them joining up with other nationalist parties for the latter. Odds are they'd be willing to come to a compromise, though.
I'm not sure if it's necessarily translation in that sense. Smjjames seems to be asserting that administratively, Catalonia would be analogous to a county in precisely the sense that Norfolk is a county in Massachusetts, or for a less ambiguous example that won't trip on the fact that Catalonia is *also* a historical county, Avoyelles is a parish of Louisiana or Denali a borough of Alaska. This is because Massachusetts is to the United States as Spain is to the European Union, and thus Norfolk within Massachusetts would correspond to Catalonia within the European Union. It's basically a straightforward cross-compare along hierarchical political lines: US = EU; US state = EU country; US county = EU province/state/autonomous community (but not a Catalonian province).
The reason I don't agree is because the analogy breaks down from the get-go, as the United States and European Union aren't entirely analogous, nor are Catalonia and, say, Avoyelles Parish. The United States does not really have autonomous governments below the state level; county, parish, and borough governments all derive their authority from the state. The major exception, that of the secession of West Virginia from Virginia, was a confederation of multiple counties in a situation where their state had already seceded from the Union. As such, it'd be more accurate politically to assert that Catalonia within Spain is indeed closest to a state (say, Massachusetts) within the United States, where the EU would be analogous to NAFTA. This also has the benefit of also being more accurate economically, as Sheb also noted. Finally, it also avoids the question in this analogy of what happens when you get below this level, where you start running into oddities like an EU city being compared to a US neighborhood or an EU house being compared to a US room.
EDIT: Added an exception to the rule, since the US is ornery that way.