Suburbs are always going to be more hostle towards pedestrians and cyclists, and we are currently seeing a trend of people moving away from them.
Unfortunately design is often used as a tool to judge others. I had the chance to study art history, but that does not give me the right to make broad and generalized statements about where people live and what they choose to do with their lives and money.
If we want to see the ugly American McMansion go away, we should spend more time coming up with good designs that fit the needs of the people who buy them, rather than trying to convince them that what they currently own Is ugly.
Apple did this with great success. They built a product that the consumer didn't know they needed. They imparted their design principles on the public through a solid product line, rather than telling them their current computer were ugly.
People might not need McMansions, but they are still going to want then. Until there is a better design for the same price, people are going to buy them.