The per capita differences of several aviation quantities between privately-run ATC in Canada versus government-run ATC in the United States:
Canada: 984 people per registered aircraft.
USA: 1523 people per registered aircraft.
Result: Canada has significantly more aircraft per capita than the USA.
Canada: 519 people per licensed pilot.
USA: 550 people per licensed pilot.
Result: About the same per-capita rate of licensed pilots. Tiny edge to Canada.
Canada: 24,438 people per listed airport.
USA: 23,785 people per listed airport.
Result: About the same per-capita number of airports. Tiny edge to USA.
My conclusion:
Anyone claiming that aviation in the USA is somehow more robust than anywhere else in the world probably hasn't done any statistical comparisons.
And anyone claiming that privatization is bad for general aviation is probably an unwitting tool of the business jet lobby, which pays for about 1% of ATC costs while using about 15% of its services.[7]
These are the raw stats and the references I used:
Canada
----------
Population: 35,850,000 [1]
Registered Aircraft (2016): 36,448 [2]
Licensed Pilots (2016): 69,012 [2]
Airports (2013): 1467 [3]
USA
-----
Population: 321,400,000 [4]
Registered Aircraft (2014): 211,084 [5]
Licensed Pilots (2016): 584,362 [6]
Airports (2013): 13,513 [3]
[1]
https://www.google.com/search?q=population+of+canada&ie=utf-8&oe=utf-8[2]
https://www.tc.gc.ca/eng/policy/transportation-canada-2016.html#air-transportation-sector[3]
https://www.cia.gov/library/publications/the-world-factbook/fields/2053.html[4]
https://www.google.com/search?q=population+of+united+states&ie=utf-8&oe=utf-8[5]
https://www.rita.dot.gov/bts/sites/rita.dot.gov.bts/files/publications/national_transportation_statistics/html/table_01_11.html[6]
https://www.faa.gov/data_research/aviation_data_statistics/civil_airmen_statistics/[7]
http://reason.com/blog/2017/06/23/rural-senators-and-private-jet-operators