As we know, the Americano begat the Negroni when the bartender replaced the soda water in the drink with gin for Count Cammillo Negroni.
Then supposedly another bartender mistakenly poured prosecco into a Negroni instead of gin, and the Negroni Sbagliato was born.
I think if that happened to me (though I can't imagine how I'd confuse gin with sparkling wine) I would still name the drink the Deluxe Americano (or its Italian equivalent) as it seems more true to that recipe than to the Negroni.
But I don't make the cocktail naming rules, yet.
Anyway, I write about the Negroni Sbagliato in my latest post for Fine Cooking. Go get some.