Americans are becoming more complacent. People socialize with similar folks on Facebook and get food delivered through Uber while sitting at home streaming Netflix. Folks medicate themselves more, keep to themselves and move less often. This isn’t the same restless America whose grit helped transform a British colony into a major superpower. Economist and blogger Tyler Cowen explores this theme in his new book, The Complacent Class: The Self-Defeating Quest for the American Dream . An economics professor at George Mason University, he is also chairman of the university’s Mercatus Center, a free-market think tank. Cowen recently spoke on the Knowledge at Wharton show, which airs on SiriusXM channel 111 . An edited transcript of the conversation follows. Knowledge at Wharton: Explain this need that people have for comfort and security in our society. Tyler Cowen: American dynamism has been declining for several decades. We now have a society where we’re afraid to let our children play outside.…