Norway and the US have endless differences, and many that affect salary. Trying to tease out the effect of just one difference is a significant project.
I've been an employer. I know for a fact that I'd think twice, three times about hiring somebody if I knew it would be hard to get rid of them if they don't work out. (Such as a requirement to document the poor performance would be - that can take months.) I also know I'd make a lower offer. You would, too, if it was your money paying their salary.
And I know that I would be willing to accept a lower salary in order to reduce bullshit conditions on my employment, like being fired because the boss doesn't like what I do on my own time, having to work with people that the boss wants but is incompetent (and possibly be fired due to nepotism), forced to decide between working extra hours over being with family, etc.
I know that I am not alone in thinking this.
You have pointed out one factor. Others, including jernfrost's account of Norwegian conditions, have pointed out that there are many factors. I've specifically argued that your observation is not significant enough to set policy decision. Now you agree that there are many factors, so do you agree that one point that you bring up might not be a useful one?
You give your experience in the US workforce, but your original observation concerned how you thought it would affect the Swedish workforce, with the implication that it was a significant universal principle.
I've been an employer. I know for a fact that I'd think twice, three times about hiring somebody if I knew it would be hard to get rid of them if they don't work out. (Such as a requirement to document the poor performance would be - that can take months.) I also know I'd make a lower offer. You would, too, if it was your money paying their salary.