I've been googling stuff up about couple of countries and their broadband technologies / cultures and have some info on Japan, tho not as an expert :-)
In Japan, virtually all metropolitan areas (and if you bother to look at Japan with Google Earth, you can see that pretty much the whole country is equal to a metropolitan area ;-) are covered with 100Mbps or 1Gbps fiber-optics that have already replaced DSL lines as the most popular methods of connecting to Net.
There are couple of reasons for the difference:
1) Like in many European countries, the telephone companies who owned the cables were forced to open them up to competition for reasonable price, thus creating competition for consumer connections without needing to build massive infra for each competitor. Thus, allowing even small companies to compete for customers with reasonable prices (say, $22 per month, including taxes, for 100/100Mbps connection :-).
2) Much, much more densely populated than virtually any Western country.
3) Government has set certain goals for the country's Net connections that operators must achieve, such as the availability for whole population by certain year and certain speed targets.
Another good example for a country with super-fast and relatively cheap connections is Sweden, where govt is subsidizing fiber-optic connections and making them available to even the most remote location in the country. With Sweden, this is quite interesting, as the country has very low population density -- much lower than U.S.
