When people refer to Scotch whisky, they spell whisky without an ‘e.’ When they refer to the same golden or amber elixir produced in the United States, they spell whiskey with an ‘e.’ What gives?
As it turns out, the original spelling of the spirit is whisky without the ‘e.’ However, sometime in the 1800s, American distilleries wanted to differentiate their product, produced in similar fashion, from the Scottish version. In general, Scotch Whisky is spelled without an ‘e’ and any other whiskey (Canadian, Irish, etc.) is spelled with an ‘e.’ It’s unclear where the Japanese single malts fit in as they go without the ‘e.’ (Yamazaki for example)
Of course, this is not a rule followed universally and there’s no way to enforce it. In fact, a Boozin’ Blog they looked at the Alcohol Tobacco and Firearms guidelines, to see if they required any nomenclature rules, and saw no consistency either.
In the end, tradition and ceremony dictates that Scotch is whisky without an ‘e’ and everything else has an ‘e.’