Answers to questions like these are always going to be pretty speculative, but I think there's a few probable reasons:
European countries, even if they weren't very powerful, were treated with at least some pretense of civility, while you just took whatever you wanted from third world ones.
Also, when social democracies started to form in Europe, the US was just starting to exert it's influence over the area. Other European countries like France and the UK still considered themselves powerful empires with overseas territories, and would probably not like it if the US started to meddle too obviously in countries in their neighboorhood, which were also members of stuff like OEEC .
Finally, Norway was a country with a tiny population with poorly developed industry and not a lot of notable natural resources (until they found oil in the 70s) which was mostly true for the rest of Scandinavia too. There's just not that much actually worth exploiting when you risk alienating countries that are valuable as military allies against the Soviets because of their location.
Also a fun fact: the European social democracies weren't free from meddling either. The post-war government in Norway wanted to organize the contry as a planned economy, but were convinced not to as a pre-requisite for being a part of the Marshall plan.
until they found oil in the 70s
this is the really important part. the exploitable resource came after political considerations overruled abusing their political system
back when Norway was pisspoor fisher country the rest of europe didnt really give a damn about treating them well, into ww2 they were disposable and bully-able it just wasnt worth it for most except immediate neighbors
Norway can't grow bananas.
They already had strong national capitalists instead of rural oligarchs ruling all. Their oligarchy understood that moderate fascism was the best way to prevent revolution.
The goal wasn't to prevent social democracy in south america because it would led to gommunism (rather the opposite) but because it would led to industrialization and so competition.
Local industries would not only produce the stuff the peasants needed, but would also use up the cheap resources imperial companies were stealing from there for pennies.
The latam rural oligarchy agreed to not having local industry because they didn't care, they had their latifundios, having industries led to strong unions and shit, pure nuisances, let's just relax and whip our slaves.
Plus, to have industries you need engineers and stuff, but we don't have many cuz those grow in universities, but those shits are expensive (no way we are building them and giving free access to the proles) so only rich failsons go to universities and they obviously do so to become lawyers and then politicians. Maybe from time to time some nerd second-son studies some medicine but that's it.
I think you know
However, South America was also unique in being in the the US’ sphere of influence. I wonder if they would’ve treated Europeans the same way if there south of the US
Just listen to the most recent cush log you will get more then your fill not even joking its like what the whole episode is about almost
https://m.youtube.com/watch?v=y9pEUf6epJY
