One thing I section I came across recently seems contradictory on this point where "alcohol" is specifically mentioned.
§ 4.21 The standards of identity.
...
(g) Class 7; aperitif wine.
(1) Aperitif wine is wine having an alcoholic content of not less than 15 percent by volume, compounded from grape wine containing added brandy or alcohol, flavored with herbs and other natural aromatic flavoring materials, with or without the addition of caramel for coloring purposes, and possessing the taste, aroma, and characteristics generally attributed to aperitif wine and shall be so designated unless designated as “vermouth” under paragraph (g)(2) of this section.
(2) Vermouth is a type of aperitif wine compounded from grape wine, having the taste, aroma, and characteristics generally attributed to vermouth, and shall be so designated.