Why is the primary form of travel in the United States personal vehicle rather than by mass transit?
One reason that mass transit isn't as popular in the United States is that many large cities were built with vehicles in mind thus leading to transportation optimized for vehicular transport. Another reason is that American citizens are much more tolerable or longer travel times, often traveling more than four hours just to visit friends and family in neighboring states.
Instruction: Why is the primary form of travel in the United States personal vehicle rather than by mass transit?
Context: 
Response: One reason that mass transit isn't as popular in the United States is that many large cities were built with vehicles in mind thus leading to transportation optimized for vehicular transport. Another reason is that American citizens are much more tolerable or longer travel times, often traveling more than four hours just to visit friends and family in neighboring states.