In Europe and much of Asia, they have no more space to build the type of expansive airport that can support large numbers of takeoffs and landings per day. As a result, the only way to increase capacity is to fly larger planes, hence the reason why the medium-range version of the 777-300 has sold very well in the Asian market and why the majority of Asian airlines are buying the A380-800. Here in the USA, we have a very large number of airports with commercial airline service operating point-to-point flights, hence the reason for the success of Southwest Airlines, JetBlue Airways and AirTran.
There are already quite a few old air force bases available in Europe to be converted into airports. A lot of the difference has to do with less centralized political and economic systems in the US compared to Europe and Asia. The US tends not to favor economic development of its capital at the expense of other parts of the country unlike France and other countries.
Bingo!