I don't know how accurate or up to date this is, but here is an itemization of state marriage laws with respect to age. In Tennessee, if you are under 16 a court needs to first approve the marriage. I'd be interested in how many such applications are made, and how many are approved. Some laws just hang around because nobody's using them.
As far as Polanski goes, this is all beside the point. As I said earlier, I'm surprised at some of the things I'm seeing here. I think we've lost some perspective. He was not her husband, nor her fiancee, nor her suitor. He was a grown man. She was a little girl. (Yep, 13, a little girl.) He asked her to undress for photos, gave her alcohol and drugs, and then had sex with her, utilizing various options on the usual sexual menu. That just doesn't pass the smell test with me.