South Korea: total road network: 102,062 km, Population: 48,379,392 ~475 people per km of road. GDP - per capita: $27,100 (2008 est.)
Japan: total road network: 1,196,999 km Population: 127,288,416 ~106 people per km of road. GDP - per capita: $35,300
United States: total road network: 6,433,272km (2004); Population: 303,824,640 ~47 people per km of road. GDP - per capita: $48,000
Data from: https://www.cia.gov/library/publications/the-world-factbook/
PS: I still think our network is pathetic.