AMERICAN WHISKEY IS a distilled beverage produced from a fermented mash of cereal grain produced in the U.S.A. American whiskey with added flavors and/or aged in wine casks requires reliable kosher certification. Products labeled as “straight” whiskey seem to pose little kashrus risk and are considered acceptable by most major kashrus agencies even without a hechsher. White whiskey and moonshine require a reliable hechsher. These are not regulated in the same way as regular whiskey and there could be concerns of shared equipment as well as added flavors.
Bourbon is an American made whiskey that must contain at least 51% corn in its mash and must be aged in new charred oak barrels. Unflavored bourbon poses little kashrus risk and is considered acceptable by many Poskim even without a hechsher.
Any chometz owned, produced, and/or aged by Jewish owned companies are forbidden as chometz she’avar alav haPesach (unless the chometz was properly sold). This includes liquors that contain chometz. There are a number of liquor companies in the United States that are owned in whole or in part by a Jew and, therefore, may not be consumed year-round. As this is an ever-changing landscape, it is difficult to list exactly which companies are problematic and which are not. One should do their own research and/or consult with a kashrus expert.