My experience with tequila is limited to tequila shots, a cake recipe that uses tequila, and a fish recipe that uses tequila. And there is a lot to know about tequila, so I'm just going to point you to two really good sites about tequila, both of which do a great job at explaining the different types and the tequila-making process. If you're interested in learning more about tequila, check out Tequila Source and Tequila.net.
So while I'm confused why the US has a National Tequila Day when tequila is from Mexico, I'm just going to shake my head and accept it as another national food observance that makes no sense. But I did find it interesting to learn that there is a drink called Temequila, which is an agave-distilled spirit made in Temecula, CA.