Maybe this is already clear, but in the US "tax witholding" done by your employer is mandatory for most people. So all the paperwork we do at filing time is just to compute the difference between what was withheld and what you owe.
I don't envy it at all either - but it's also because theirs is so much more complicated that even if you consider it broadly the same principle, far more Americans fall into the needing to self-assess (as we call it) category since, for example, they have 'a whole bunch of deductibles'.
IIRC, the vast majority of americans use 1040 and 1040EZ. Both of these can be automated.
Norway just asks upfront. Yes, I have to try to predict what I'm going to make that year, but yes, I can update it if I change jobs. Marriage, children, etc all gets factored in. If I don't change things, I think it stays the same. The vast majority of folks don't have to self-assess like Americans do, and thinking that we need to do it more seems to be more leaning towards an attitude of Exceptionalism - which seems to be just as much an excuse as it is something folks have pride in.