On the Fact that Harvard Epidemiologist Professor, Martin Kulldorff, Recently Did an Exhaustive Analysis of Mask Mandates In Various European Countries and U.S. States and Has Concluded that Masks Do Little to Nothing to Stop the Spread of COVID-19, Surprise, Surprise - https://thefederalist.com/2020/10/29/these-12-graphs-show-mask-mandates-do-nothing-to-stop-covid/

There are tons of graphs in this article and they all clearly display that COVID cases skyrocket after these mandates and that when you compare various countries and states with and without the mandates there is either no difference or the non-mask mandate regions actually do better. No, it's not definitive evidence in that there isn't a controlled study but you'd that there would be at least a few locations yielding a positive result and it just isn't there. Sorry but, no.