Unfortunately the wayback machine didn't cache the CDC's page on guidelines until recently, but an article in US based Vox from February says: https://www.vox.

Unfortunately the wayback machine didn't cache the CDC's page on guidelines until recently, but an article in US based Vox from February says: https://www.vox.com/recode/2020/2/13/21128209/coronavirus-fears-contagion-how-infection-spreads https://www.vox.com/recode/2020/2/13/21128209/coronavirus-fe... "Currently, the Centers for Disease Control and Prevention (CDC) advises against people in the US using face masks because most people who aren’t trained medical professionals may not know how to fit them properly, and the risk of exposure in the US is so low to begin with."