This isn't "supernatural punishment". It's sentencing for more than one crime. Life, probably for murder, plus 20 for (say) armed robbery. It's not meaningless to tack on those 20 years. If the murder conviction is overturned, so is the life sentence, but not those 20 years, unless those convictions are also overturned.
Some of these (10,000+ years) read like something from a harry potter novel, not a realworld justice system.
https://en.wikipedia.org/wiki/List_of_longest_prison_sentenc...
Life + 20 is a completely different class of sentencing than the ones in the Wikipedia list. I don't see a large distinction between re-sentencing or not. The end result should still be 20 years, no? "Life without parole + $X years" is functionally equivalent to a "whole life order" in the UK.
The extremes in the list are of two classes:
1. Mass murderers, serial murders, or others who have gone on large crime sprees. These generally carry life sentences without parole. So, they cannot be indeterminate no matter how many years are tacked on, unless they have a successful appeal of all convictions that result in life sentences.
2. The indeterminate sentences you're talking about. Generally speaking, these are pretty egregious, violent crimes with many victims or the same victim over a long period of time. In many cases, the convicted could have received a life sentence, or one would have been mandated depending on the crime and the state.
But this isn't common by any stretch, except on TV crime dramas. A problem is the giving of life sentences to nonviolent offenders (e.g. California's three strikes law). Also problematic is the stacking of charges to compel plea bargain, which is exacerbated by cumulative sentencing. But "Life + 20" is just, effectively, a life sentence with a different label.
The perception of rights goes both ways. Canadians sometimes laugh at the US legal system. Canadians see crimes like felony-murder or misdemeanor-manslaughter as ridiculous. So too with the American tradition of supernatural punishment (ie "life plus twenty"). And the duel-sovereign thing, the risk of being tried in state and then again federal court, is very strange outside the US.
The biggest cultural difference has to be the levels of incarceration. As the US increased punishment in recent years, Canada did the opposite. Have a look at their military prison. It is more often than not empty. https://globalnews.ca/news/4097208/military-prison-edmonton-...