You're saying that most Americans think that unmarried women who take responsibility for their contraceptive health are promiscuous?
I'd like to see that proven in some way.
Do you have any evidence that this is the case?
See, I would suspect that most Americans would simply think that we're talking about women who are generally pretty monogamous but are, nevertheless, sexually active.
That's the boat that almost all adult women that I know, heck that I've ever known, fall into.
And unless you're a lunatic fringe fundamentalist Christian conservative, or a Muslim (two peas in a pod in many, many respects), you don't automatically conflate monogamous sexual activity out of wedlock with promiscuousness.