Cars are a necessity in the US. We have more room and things are much father spread out. Try getting around a typical western US city without a car.
That's not because you have more room. That's because public transportation sucks and has a social stigma.
You don't need a car in London, for example.
While I do not disagree with the social stigma associated with the use of public transit, the real problem in these Western US cities is poor urban planning. Much of the growth in the West has been over the last 20-40 years and coincides with the heyday of the automobile, unlike their Eastern counterparts, which formed before the advent of the automobile. Many of the Western cities chose to grow outward instead of upward, that is, they grew in terms of area but not density. This is due to the choice to build large tracts of single-family homes and strip malls instead of multiple-unit and mixed-use dwellings, which effectively decrease density of the region. And no public transportation infrastructure was built to accommodate the influx of new housing, instead efforts were focused on expanding and building out the existing roadway and freeway networks.
The problem then becomes that as the area a city covers expands outward and new residents populate these areas, many of them still commute back to the city center for work, clogging the highway network beyond its design capacity but with little room and money for expansion. Many people braving these commutes would not mind using public transit but it is not feasible in their area and the cost to build such a system is more than most governments can afford, especially in these economic times.
This is not intended to bash all Western cities. In some cases (see San Francisco and Portland OR), cities have implemented stricter zoning requirements and urban growth limits, forcing developers to invest in multiunit dwellings and mixed-use space. These cities have also invested greatly in a public transit system, including taking steps to reduce or eliminate much of the "social stigma" associated therewith.