Go further back. The Civil War could be viewed as large-scale tribalism. After that, there were regional and ethnic tribalisms. The World Wars pushed us into a bigger tribalism - the US became one giant tribe. (It still had the smaller tribalisms, but they became less important.) That kind of held through the 50s. In the late 60s, the hippie movement could be regarded as a new tribalism (and a rejection of the old one). The US "big tribalism" has been progressively fragmenting into a number of "small tribalisms" since then.
