Does anyone know how long it takes for radioactive isotopes resulting from an above ground nuclear explosion to travel world wide?

After seeing the alleged Ukraine nuclear explosion (I am skeptical), I've been watching my geiger counter, but so far it remains at a steady one banana day equivalent (.1 microseverts/hr).

I am wondering if an above ground nuclear explosion occurred, how long it would take to get to me, I'm in the USA. I know that when they were doing above ground nuclear testing in Nevada, it exposed film in New York so that was a non-trivial amount of radiation they dumped on the American public. If it was enough to expose film, I would certainly expect it to be detectable on a Geiger counter even around the world.