What's the deal with airplane food? (asked with a Jerry Seinfeld inflection). I second Buyno Wino's comments. Champagne is a sparkling wine from the Champagne region in France. Champagne is a sparkling wine. Sparkling wine is not necessarily Champagne.
But in many regions of the world, Champagne has a somewhat generic meaning. In the US, winemakers often label wines as Champagne, even though they are not technically Champagne. US regulation allows use of this term as long as the actual location of origin is clearly shown on the wine label.
Yes, Champagne can only come from Champagne and it must be done in the traditional method where fermintation takes place in the bottle. Most wine that is not from Champagne but is done in the traditional method is noted as such on the bottle. Other sparkling wine note noted as produced in the traditional method and sparkles like Cava and Prosecco are fermented in a tank.
But in many regions of the world, Champagne has a somewhat generic meaning. In the US, winemakers often label wines as Champagne, even though they are not technically Champagne. US regulation allows use of this term as long as the actual location of origin is clearly shown on the wine label.