This article says that the trend has started since 2013. In what way has American individualism changed since then? I would say it hasn't. How could American culture shift that much in less than 10 years in this specific span? I don't buy that explanation without more thorough study.
American individualism has existed far longer than the data in this article. We've been sitting in cars by ourselves since the mid-century. I am most skeptical about easy and simple explanations like the one you're describing.
For one thing, I'm looking through the data and I'm struggling to find the data that the chart is representing: https://www.bls.gov/tus/database/tustabs.htm
Is anyone else able to find it?