I'm old enough to remember when go karts were a lot less stable and would roll if you got bumped in a turn. Inevitably, somebody would stick out their arm as they started to roll, and broken collar bones were not uncommon.
It sounds like a minor break and the kid should heal quickly. I broke a toe in first grade, a wrist in third grade, and then fingers four times before I finished high school. Obviously, I didn't learn to be careful after the first time, but it was never more than a hassle. Kids seem unusually resilient sometimes.
@VincentMalamute There's a quote from "The Office" where Creed says "I already won the lottery, born in the U S of A" that I think about from time to time whenever I feel like we need more. Nope, we're just fine.