The first step is to get Congress to actually make child abuse a federal crime, which it should be. That seems like what Australia wants to do by making one age of consent law and making child sexual abuse a federal level offence rather than just letting each province make their own decision on this horrific crime. And even the Witnesses, for whatever that is worth, said that they would be happy if the government did that.
It is sad though that the political system in America is so broken that even for something so basic and easy to realise that it is needed won't ever pass. The two political parties can't agree on a single thing and neither trust the other not to throw on amendments that would make it so that the other party can't vote for it.