Why are infections rising again in US?

https://www.bbc.com/news/election-us-2 [login to see] 8
What's the overall picture?
With about 7.5 million coronavirus cases, the US has the highest number of confirmed infections in the world - about one fifth of the global total despite having only 4% of the population.

After the initial spike in late March, social distancing restrictions gradually brought infections to heel. By May, case numbers had stabilised. But as states peeled back lockdown measures, cases began to rise, reaching a countrywide high in July.