This is a pretty nice and very recent summary: https://science.sciencemag.org/content/early/2020/06/02/scie...
I think it can change something: currently masks are seen as a necessary evil in stores and public transport. They could and should become ubiquitous.
With mask usage in Germany I see only negative trends in the growthrate of both case and death. I think to make them work something has to be changed.
There is a good chance that it now only works as a reverse placebo - it makes people feel confident and pushes them into more risky behaviour - most likely net negative.