Champagne are not difficult to recognize... Especially if you compare them to other sparkling wines.. They probably are the easier to recognize for many people..
I found reds with a full body and particular blends much more difficult..
It all comes down to your mouth.. I could recognize a valpolicella or a chianti among any other wine because I grew up with them, but I would find really hard to distinguish a Chilean Shiraz from a Californian one..
But I'm not a professional sommelier..