Japan, South Korea, and many countries outside the U.S. have citywide Wi-Fi access because those countries often have a state run (or at the very least state supported) telecommunications "company" providing the access in a highly urban area. The economies of scale in cities like Tokyo or Seoul make it much more reasonable for a single state run telco to provide Internet access to the majority because everyone lives and works in the city--minimal effort to install access points and fiber optic cable equals the maximum result of customers served... and there's a monopoly on the service.
In the U.S., a great number of city workers live outside the city in the suburbs and commute to work in their own vehicles rather than buses and trains for whatever reason. Both those suburban and urban users have the choices of numerous Internet providers (DSL, cable, satellite, dial-up, etc.) at different price points and service levels. The power of the market and of choice...
If it was a monopoly Internet provider in the U.S. providing Wi-Fi, everyone would be up in arms because there was no choice. If a municipality such as SF or LA provided "free" Wi-Fi, they'd jack up their already sky high property taxes or sales taxes to pay for the Wi-Fi that not everyone in the city was using and/or was being misappropriated by suburbanites that came into the city with a laptop and a Wi-Fi card looking for "free" Wi-Fi.
So what's the solution to this mess?
Don't know but that's probably a topic for a future Ten ep!