I couldn't find a way to fit all that in the title, so I got 99% there and clarified in the first post. The title still has more resolution toward the full detail than the original title.
I'd suggest something like: "Japan Post stops accepting US shipments over $100."
To emphasize that it's not in effect yet and that it's to, not from.
edit: Someone went and reverted it to something less clear than everything else