The National kart racing scene is currently dominated by two major sanctioning bodies: Superkarts!USA and Maxspeed Entertainment. Superkarts!USA (SKUSA) began as a shifter kart only organization but has grown and morphed to encomass TaG racing as well. SKUSA operates a three event national tour that in 2016 will feature stops in Phoenix, Arizona, Newcastle, Indiana and Las Vegas, Nevada. The final event in Las Vegas is the SKUSA Supernationals, the largest single kart race in the world. SKUSA’s classes consist of Iame powered TaG classes for cadet, junior, senior and master’s age groups as well as shifter classes for junior, senior and masters age groups.
Maxspeed Entertainment is the U.S. organizer for the Rotax Max challenge, they oversee the regional series, the Grand Nationals, the PanAm, The Florida Winter Tour and in 2015 they launched a national series known as The U.S. Open which in addition to all of the Rotax Max classes includes shifter categories for senior and master’s level drivers. The 2016 U.S. Open series features stops in New Orleans, Lousiana, Tooele, Utah and Las Vegas, Nevada.
There are several other major sanctioning bodies, but as of now, none of them offer true national tours with a complete variety of classes. Here are some links so you can check them out for yourself.