No one is compelling one to be a Catholic in America.
So if a woman wants to have premarital sex by breaking her Catholic tradition, it is her choice to do so. She is not being forced into that faith, and she would have no compulsion to digress from the tenets of her faith.
With Muslims in Muslim societies, that is not the case. Whether a woman wishes to have premarital sex or not, she must stick to Islam, and if she breaks the adultery rule, she will have hell to pay, in those cultures.
I still don’t understand why you think Muslim girls would have sex instead of Catholics? Do you really think teenagers having sex is dependent on their religious beliefs?