Kudos for the links.
Regarding Australia, that’s a complete nonstarter here. Too much standing in its way. And as an unintended consequence Australia also saw most other violent crime (assault, rape, etc.) increase in the years since.
Interstate laws could be bolstered, but they’re not super-weak either. It just boils down to enforcement. How do you enforce it? Should we have customs inspections at state lines? So many of the laws on the books just don’t really matter (from an enforcement standpoint) until something awful has already happened.