From Wiki

Let's start bluntly. YOU NEED A CAR.

Yea, you got by being carbon neutral in London living between 5 tube stops and 10 bus lines and a rail network, but the US isn't London, and even in the best cities for public transit like NY and DC you'll quickly find that a car is kind of a nice thing to have.

In small towns, it is essential. As important as a roof over your head, a passport, and a telephone.

America is built around the car. Roads, neighborhoods, zoning (planning commission) regulations, stores and work are all focused around someone 'driving' to do these things. With the exception of a few major cities (New York, San Fran, Boston etc) owning and driving a car is *required* to do even the simplest of tasks, such as buy groceries or go out to dinner. Driving the kids to a soccer game two miles away or a birthday party across town is just part of life in America. There is no bus option to take the kids to the movies.

A common theme behind threads like 'I don't have any friends' and 'I'm so homesick' is the fact that the person is relatively tied to their houses without any means of travel. Either they live in a suburb with only a few sidewalks (pavements) or in a place that simply isn't safe to walk down the street for fear of being run over.

Seriously--budget for a car. Budget for two cars if one is going to be out of service (i.e. at work with the spouse).

Travel

America is huge. To fly from one coast to the other takes a minimum of 6 hours. To drive from one end to the other is measured in days, maybe a week. Trains take almost as long and buses (coaches) are equally slow.

By and large, if you want to get from city to city, you're looking at flying. Four hour drives are about the limit before people start to look at flying as an alternative. On the East Coast (Washington-Baltimore-Philadelphia-New York-Boston) rail is a real option, but in most other places trains are frightfully slow and the distances vast such that it is not a real alternative. A 2 hour flight from NY to Chicago is a 14 hour rail journey, and even then, you are only about 1/4 of the way across the US!

Public Transit

With the exception of big cities, public transportation is very limited in the US. While many smaller communities have buses or light rail, these are often much slower than driving yourself or are of such limited scheduling that using them is incredibly inconvenient. In rural areas there is simply no public transit, or if there is it's often referred to as the 'DUI Wagon' as the only people who use it are those who lost their license due to driving while intoxicated.

In some major cities there are 'Zip' cars, which are car-sharing rent by the hour options for vehicles. By and large this is in major cities where you can get by 6 days a week without a car (but want one on the weekend to run an errand or buy some groceries).