How frequently does an average american women engage in some kind of sexual behavior? once a day?

Varies: It varies according to age and relationship status. Studies suggest an "average" frequency for married women is about once or twice a week. Some women prefer daily sexual activity and others may have sex only rarely, like every 6 mo. Older couples may become abstinent for a variety of reasons. There is no right or wrong in terms of sexual frequency.

Depends upon age: Some young women masturbate on a daily basis, some never or rarely, they tend to do it less as they grow older. Same can be said for intercourse: young & newly wed or living together may have sex once or more daily this also slows down with age & partner's interest. So basic answer is "variable".