The vast majority of people don't wait to have sex until after marriage in the U.S. It hasn't been that way for many years.
Over 52% of all weddings in the U.S. take place between (cohabitating) couples. That doesn't include those having sex without living together. The average American loses his or her virginity at age 17. The average age of first marriage in the United States is 27 for women and 29 for men. That's over 10 years of sexual experience!
Truth be told most Christians "cherry pick" which scripture verses they will follow. I've known people who were against abortion for religious reasons but participated in pre-marital sex. As the old adage goes:
"Every Sinner has a future and every Saint has a past."
Ecclesiastes 7:20 (KJV) states:
"For there is not a just man upon earth, that doeth good, and sinneth not." The goal is to find someone who shares (your) same values!