Bourbon must be made in America. Most is made in Kentucky. Its bill has to meet the bourbon Bottle in Bond Act. There is no law it has to be made in Kentucky.
Tennessee Whiskey is made like bourbon but must be charcoal filtered - "The Lincoln County Process" which removes most of the harsher tasting components before bottling. There is at least one old time Tennessee distillery, Prichards, grand fathered in that doesn't charcoal filter.
https://beerbon.com/the-lincoln-county-process-and-the-law/
Charcoal filteed Tennessee whiskey m is smoother tasting and less harsh than any bourbon.
Much like triple distilled Irish Whisky is smoother than single processed Scotch.