What does the hierarchy of the aviation bodies look like?
Does it look like this:
As pointed out by vasin1987 in a comment to the question, each country's regulatory body has control of that country's airspace: These agencies exist in a "mesh" of coequals as opposed to a hierarchy.
The International Civil Aviation Organization (ICAO) is a UN specialized agency [which works] to reach consensus on international civil aviation Standards and Recommended Practices (SARPs) and policies[.]
Like pretty much the rest of the UN, the ICAO is more a forum for cooperation between regulatory bodies than a regulatory body in its own right.