I've seen that video. What's interesting is the camera is mounted to a 250cc kart with no front bodywork. Probably removed it so you can see his footwork. And my 125 kart is not quite that fast. But almost...
You couldn't get away with that kind of street racing in the US - too many lawsuits if something goes wrong. There's two street races here that I know of - West Lafayette, IN (Purdue Grand Prix) and Rock Island, IL. Both circuits are tight with no long straights like the one in the video. 125 shifters can run at both, but it's like driving a Formula One car in a parking lot so I stick to racing on dedicated road courses...