* It decreased trust in government by backing a policy that most now understand wasn't science-based.
* It increased the partisan divide in the country for no benefit by encouraging people on both sides to label those on the other side as "nutters."
* It probably caused some amount of real harm by causing people to think that, if they wore a mask, they were protected. This probably meant some elderly and immunocompromised people put themselves at risk when they could have avoided the risk by staying outdoors.