The inability of the US to formally approve a permanent disposal site is purely political. Still, at this point enough other countries have managed to do so that we might eventually be able to pay to export our waste to one of them instead of solving our own dysfunction.
Fortunately it is self disposing, decaying away. Unlikely plain old mercury or arsenic.
Is it geographic (we have a lot more unused/undesirable than France, for example), regulatory, etc?
We have ample deposits and (for now) easy access to Canadian deposits. I imagine that there are deals in place to secure that access at an efficient price given the national security angle at play.