How can we Americans stop this from becoming more and more common?

That sort of behavior has always been common, the number of occurrences has only increased because of increased numbers of people combined with a drastic reduction in parental monitoring of their children. The world has always been a dangerous place, parents knew that and protected their children, especially young girls, accordingly. Today parents no longer ume that responsibility and expect the government to do it for them, this is the inevitable result. The only way to reduce this sort of thing is for parents to start being parents again, simple as that.