Looking for story of teen in US then goes to Germany for pro am go cart racing. Thanks
Well there's The Racer's Chronicles by Slim Rhino.
It hasn't been updated since Feb (disappointingly) and it's actual car racing not go-karts, but it may be what you're thinking of.
https://storiesonline.net/s/12539/the-racers-chronicles-book-i-junior-formulae