American whiskies also have a few specific divisions.
"Blended American Whiskey" can be compared to brown vodka. It can be any ratio of aged whiskey to neutral grain spirits (think Everclear) and even can have color added. Really, the only thing that makes it able to be called whiskey is that it's brown, made from grain and made in the US.
"Bourbon" is much more specific. While most people think it must come from Kentucky, this is not true...it must be made in the US (there are a few legitimate Bourbons from outside Kentucky). It also must be made mostly (>51%) of corn, and must be aged in unused, charred, American white oak barrels for a minimum of 3 years.
"Rye" (short for Rye Whiskey) must be made of at least 51% rye to be labeled as such.
"Tennessee Whiskey" is almost exactly the same as Bourbon...there's just one (although significant) difference between Tennessee whiskey and Bourbon. "Charcoal mellowing" which is also known as the "Lincoln County process" is an extra step where the newly distilled whiskey is filtered through sugar maple charcoal before it goes into the barrels for aging. This extra step is what keeps Jack Daniels and George Dickel (the only two Tennessee whiskies) from being called Bourbon.
American whiskey, if you don't specify a style (like Bourbon, single malt, etc.) is pretty much unremarkable...it's what you'll get if you order the cheap stuff at a bar. Bourbon runs on the sweet side compared to others...it's a combination of the corn and the charred oak barrels (sugars in the wood get caramelized during the charring process). Rye is a little more on the spicy side.