Seroprevalence studies[1] in Italy, France, and Spain indicated we were a very long way off form herd immunity. They were in the range of 11-15%, where herd immunity would only start kicking in at about 70%. Based on cases per capita, the US might be 2-3 times higher than western Europe, but not yet at 70%.

I think the flaw in the piece is the author greatly underestimates the impact of the drastic measures we've taken to get those trends down. A lot of people are working from home, kids largely aren't back in school, and many of our other contact points outside of our households have been modified to minimize the risk of transmission. Seeing what happened to Israel when they reopened schools does not bode well for the US. [2]

Edit: NYC had ~20% prevalence in mid-June [3], after they had come back down from their peak. They've had many more cases per capita than anywhere else in the US, but their new cases have been flat since then, meaning prevalence has not increased significantly. Prevalence elsewhere in the US is likely in the 5-10% range.

[1] https://www.sciencedirect.com/science/article/pii/S004896972...

[2] https://pbs.twimg.com/media/Ees8MesX0AAbDE2?format=png&name=... https://www.wsj.com/articles/israelis-fear-schools-reopened-...

[3] https://www.cdc.gov/coronavirus/2019-ncov/cases-updates/comm...