The stuff about the USA having more room is an old myth.
I dont think thats the case
n my local area (of the US), we have four public airports within a 13 mile radius circle having a published total of 2011 operations on the average day. Within that circle there are also two busy military airports with unpublished traffic volume. FYI. All the airspace within the area has radar coverage for IFR traffic, no Class G..
So it all takes place within controlled airspace with Radar, So the US system would not work here as we have class G and units operating without radar.
Most of the traffic is within an 18 hour day. Using 2300 operations over that period to include the unpublished military traffic, it comes out to roughly two new operations per minute within the 26 mile diameter circle.
I'm wondering how that would compare with the busiest areas of UK, greater London for instance.
I think heathrow does roughly half that over a 24 hour period, throw in London City and Biggin Hill within the greater london area and you'll well outstrip that number, plus the various aircraft transiting the area.