At just over 1g a week, it's not out of the realms of possibility, taking into account those who abuse it. I've unfortunately known people who could use that much in a week.
What I absolutely do think it's out of the realm of possibility that the average American does. Something like 2% of Americans use cocaine.[1] That figure is probably extremely imprecise, but it barely matters because even if it was 20% it would require that the average user was going through a gram a day.
[1] https://en.wikipedia.org/wiki/Cocaine_in_the_United_States