
Cherry bourbon is a flavored spirit on a bourbon base with cherry (often black cherry) added.
Bourbon under cherry and sugar, and the sugar is what a plain whiskey leaves out. About a third of the volume in a cherry liqueur brings back the fruit and lands near the usual strength.
Straight bourbon with nothing added, so it is drier and stronger. Swap it in and the drink loses the cherry and a good deal of sugar, which has to come back some other way.
Cherry liqueur is defined by flavor and sugar, and its spirit base can be anything; cherry bourbon is defined by the bourbon underneath. The liqueur is sweeter and weaker, so a drink built on the bourbon loses both its backbone and its dryness.