Napa Valley is now recognized as a Geographic Indication (GI) in Europe. About time. The Frogs have bitched (rightly so) about their Champagne for years. Which is why an American, or other non-Champagne region, sparkling wine is not called "Champagne." These wines will usually say "methode champagnoise" instead.
In all, it is good for the consumer to know what he or she is getting.