they can't consent to sexual relations.

That's seriously harsh. Not just the parents but the law deciding when you're allowed to have sex? No surprise that teenager's gain a reputation for rebelliousness.

Yes, the US is one of the more puritan "Christian" countries. In the US, two teenagers cannot have consensual sex together, by law. If they do have sex, they are both punished. (Some states have recently passed exceptions that tend to start at age 16-17, for couples that are of the same age. Even then, two 17 year old can have sex but an 18 year old can't have sex with a 17 year old because one's a major and the other one's a minor. Choose your mate's birthday carefully.)

As an aside, many US teens who took nude photos of themselves and gave them to their boy- or girlfriend have been charged with the high crime of distribution of child porn. Here is a report on one such Florida couple, aged 16 and 17, who were convicted (on the appeal, too). They kept the photos for themselves, but someone tipped off the police, the court record doesn't say who - possibly the parents. The appeal judge wrote in his opinion that one reason he wanted to punish them was that if left alone they might in the future sell their photos to child pornographers to make money.

The CNET article doesn't say what their punishment was, and anyway it was a random Google result out of at least dozens of similar cases, but I would imagine registration on the sex offender list for many years - which takes away a lot of rights no matter what your age - and jail time and/or probation and/or whatever they tend to give to 17 year old felons in Florida.