Let's not get confused in statistics which truly are apples with elephants.
It's not really, it's numbers of flights per ATC. It's actually pretty simple.
Australian figures for aircraft include those with self administering organisations (gyros, ultralights etc) which in the main do not use Controlled airspace; US figures are diffferent.
True, though the US figures do include 34K experimental category aircraft.
ATC numbers depend on who you count. Those on a service provider payroll (Here one plus RAAF, There many providers) -and
are you counting console workforce or those with a licence...... EG I have an ATC licence but I have not sat at a console for some years now. Even here AA have many licensed controllers doing administrative jobs not separating aircraft.
Example: Their CEO holds (or has held) an ATC licence but I'll bet he has not sat at a console for a while!!!!
I'm just quoting what AsA and the FAA say. AsA say they have 1000 ATC. If not all of them are sitting at a console, it just makes the numbers worse for those that are. Perhaps the FAA counts ATC the same way? There would have to be an awful lot of them on other duties to make any difference though.