It sets down the rules for which civil aviation (including unmanned free balloons) follow. You could argue that "a balloon launched in Illinois and found in Alaska is within the US"... but it transited other countries airspace (there is no way for a balloon from Illinois to get to northern Alaska except the long way around) and should have been following the rules there.

And so, the question that I'll ask - "did the people launching balloon obtain permission to launch from the United States and prior permission for countries that it passed over?"

This isn't exclusively a weather balloon - which has a different carve out for permissions.

But it is an aircraft that traveled internationally and through the airspace of multiple different countries.