Your idea of statutory rape not being rape fails at the definition you specified for the former term. Someone below the age of consent has been deemed by the law to be unable to make an informed decision about their body - which is true in all cases; in cases where that may not necessarily be true, the child would be smart enough to realize the act they're engaging in is unhealthy if not for their development then for their partner. Sexual relations with someone who cannot consent is rape. This doesn't include the fact that a large age discrepancy between two parties engaging in sexual relations will generally lead to an inequality in power, and sexual relations between two inequal parties in that way may not be rape but certainly isn't "good sex".
Many states have "Romeo and Juliet" laws, which decriminalize sexual relations between people under the age of consent as long as they're similarly aged, solving the biggest issue most people have with the idea of statutory rape ("what if children rape each other?").
I use the term "sexual relations" because the act of sex necessitates consent. And although sexual relations with children may be uncommon outside of the "Anglo bubble", they still harm the child whether via physical or mental trauma.
Lets be clear here. When you say child you're referring to teenagers, not prepubescent children.
The question is whether or not a 15 or 16 year old can consent to non-harmful sex, and the answer is obviously yes. At that point they are sexual creatures with their own urges. two 16 year olds having sex is not harmful in any meaningful way, many many people start having sex at 16 (or younger) and go on to be just fine.
At this point, as far as I'm concerned, it's been clearly established that young people under the age of consent _CAN_ actually consent to sex.
Statutory Rape is not about consent, it's about manipulation. Due to the differences in life experience between a 16 year old and a 20 year old, the 20 year old can manipulate the 16 year old to give that consent. This does not imply that the sex between them is implicitly harmful to the 16 year old, just that it's immoral for a 20 year old to do this sort of manipulation.
It's also clear that a 20 year old can rape a 16 year old. Actually rape. And they'll be charged with rape, regardless of the age of consent. This is because, by definition, with statutory rape the 16 year old DID consent.
And one last piece of evidence to show clearly that you are wrong here.
It's possible for 2 25 year olds to have sex and statutory rape charges be brought. How? Because one of them is mentally handicapped.
Because Statutory Rape is not specifically about the age of consent, or giving consent. It's about the coercion of someone who is not considered mentally capable of protecting themselves from said coercion. It's about the morality, not about any sort of inherent harm of the sex itself.
And to head off one argument that I KNOW is coming. The age of consent in Japan is 13, pointing out that the age of consent is 16 in many places in western civilization is not meaningful or useful here. It doesn't change the ideas that I've presented in this post.
Many states have "Romeo and Juliet" laws, which decriminalize sexual relations between people under the age of consent as long as they're similarly aged, solving the biggest issue most people have with the idea of statutory rape ("what if children rape each other?").
I use the term "sexual relations" because the act of sex necessitates consent. And although sexual relations with children may be uncommon outside of the "Anglo bubble", they still harm the child whether via physical or mental trauma.