In the US there are 7234 institutes and 183 889 000 working age population (19 - 65). That is 25 420 person per institute (source: https://nces.ed.gov/fastfacts/display.asp?id=84 and https://www.census.gov/population/age/data/2011comp.html).
However in the Netherlands there are 56 institutes for 10 065 804 working age population (20 - 65 years), resulting in 179746 citizen per institute.
Now in the Netherlands the tuition costs are low (around 2000 euros). But in the Netherlands students are sorted in middle school already, put on different tracks that determine if and what kind of university they can attend. So the real pool of potential students is lower than the pool of working age population.
Feel free to add numbers about other countries in this google sheet: