Seems about right to me, if not high. Keep in mind that this isn't the number of Americans that consume alcohol, but the number of Americans that consume alcohol on a daily basis. People that drink on the weekends, or a few times a week after work, don't qualify. 1 in 20 seems a bit high to me, but within the ballpark.
This thread is fascinating for highlighting that what seems normal to one person seems rare to another.
I'm not sure I know a single "daily drinker". Even the people who had reputations as being heavy drinkers I don't think drank every day. Drinking daily sounds like something someone in recovery would talk about as the final stage of their spiral towards rock bottom before they went to rehab, not something I'd expect 1 in 20 people to be doing.
But maybe I'm underestimating how many people have one glass of wine with dinner or one beer after work.
Before becoming a techie I did construction work and nearly every person drank beer after (and often during) work. It was a way to alleviate the pain from hard manual labor.
I think there's a lot of people that drink a glass of wine at dinner maybe? They're not by any means alcoholics but would be included in that 5%, which seems expected I guess.