I'm sure Aussie, in fact I know aussie air traffic controllers are good but 8 hub airports? If you include cities the size of darwin and hobart in these stats then you've probably got at least 200 or more hub cities in the USA. The high density area in the US (assuming this is the eastern seaboard) has about 2500 flights in the air on a given morning. The E gates at O'hare are busier than YBBN. I'm guessing europe would probably be the same.
Aussie controllers are good but I think this is accredited to the fact that there hasn't been a large catastrophic air accident in Australia's past. Not the number of a/c they push around the sky.