USA seems to be one of the least regulated countries when it comes to amateur ballooning. Under FAA rule 101 exceptions, a tiny balloon can be launched without notice, probably due to the vast geography and airspace that USA possesses. I have been doing it myself and in most of the Europe, normally, a NOTAM is required at least few days in advance and aircraft are to coordinate their actions based on the location of the balloon launch/flight path. It is nevertheless a fun, inspiring and niche hobby, when something takes off of the palm of your and and flies around the planet few days later.
