As counter intuitive as it sounds there is reason to believe that currently the penetration of the disease is much lower than in March.

The modeling from IMHE claims that in March the number of daily new infections were above 250K whereas today are about 120K.

https://covid19.healthdata.org/united-states-of-america

see the tab called Infections and Testing

It just that we were measuring a lot many more people now. But it is true that in June there were fewer cases than today, but by far the most cases were in the Winter.

How else would be in the situation where 10% of population is already seropostive and at least as many don't develop antibodies since their symptoms are mild, thus we are probably over 20% of people having had the disease.