What countries have done the best job at tackling nuclear waste? What power-generating corporations have done the best job at owning their waste? And how many have been able to responsibly do so without it turning into a vast political issue?

The US may be fucked & awful here, but I cannot imagine the rest of the world is particularly less fucked or less awful. I'm sure some folks have not gotten quite so tied up in this question, but I also don't have high confidence they have been paranoid & political enough about how properly they ought to be dealing with waste that will live for hundreds of thousand of years. If they have to come deal with really awful problems in 20k years, at enormous expense, well, that factors against the advantage of nuclear power too.

Finland is probably the most advanced with regards to permanent geological storage.

https://www.youtube.com/watch?v=kYpiK3W-g_0