Nationally that may be a contributing factor, but in hotspot states, the % of tests which are positive has actually gone up significantly: https://coronavirus.jhu.edu/testing/individual-states and select Florida or Arizona
https://www.tmc.edu/coronavirus-updates/tmc-daily-new-covid-...
You can also correct for the sampling rate bias by looking at the number of cases per 100,000 tests (or similar). Does anyone have a link tracking that? EDIT: percentage positive tests: https://coronavirus.jhu.edu/testing/individual-states
https://www.popsci.com/story/health/black-lives-matter-prote...
If the protests were a hotspot for new infections the states that are doing contract tracing should show that. I haven’t seen any evidence of it.