Have you ever considered a thing so long that you came back to where you started from the other side, thinking maybe you had it all wrong in the first place? I've been thinking. The topic remains Scotch ale, a style that seems pretty clearly invented by Americans. Therefore, we consider this an inauthentic style, one invented from ignorance.
In the early days of American craft brewing brewers had only fragmentary information about world beer styles and the history of beer. Drinkers had even less. Many of the early beers were not brewed to style nor made with methods appropriate to style. (Old-timers will recall "pilsners" made with ale yeast and American two-row malt.) The market has matured, though, and now brewers and drinkers have a far better sense of style. Breweries were doing some pretty terrible things in the eighties, so this was an important corrective.
On the other hand, “authenticity” isn’t as obvious as it looks. Consider this thought experiment. What if, in the 1980s when Scotland was enjoying its own craft brewing renaissance, the first breweries had decided themselves to add peat-smoked malt to their grists? It would have been a perfectly native instinct—malteries were already producing the product for distilleries. What if Scottish breweries had tried to distinguish their beers from English beers with this small change? We would surely now be discussing the necessity of using peated malt in the recipes for authentic Scottish ales. Instead, it was Americans who did it, and the whole thing now strikes some people as a shameful example of brewing juvenilia. But is it, really?
There's an interesting complication to all of this. Peaty American Scotch ales are pretty tasty--and popular. For Americans, a bit of smokiness is what defines Scotch ale and what they expect. Because of this, I can't imagine breweries abandoning peat-smoked malt, at least not in those pretty popular extant brands. Which likely means that in two or three decades, peaty American Scotch ales will have been around so long no one will remember or care that there was something embarrassing about all of this. They'll just enjoy the beer and think nothing about its ahistoricity. We'll have a new style, and it will have become as authentic as any other.