Sweden abolished slavery/serfdom in the 14th century, then there was a black plague and population declined. Then Sweden became an Empire all of a sudden, not too long before USA became a thing. I'm pretty sure Sweden is the same melting pot as any other place on Earth that's moderately habitable. The difference is only scale, recency, type.
And even before all that there was a large influx of people from Russia, not to mention "viking" raids, which often brought back people of vastly different cultures.
There's probably a point to be made for airplanes vs boats, but the principle remains the same - there's the pot that's boiling hot and full of colorful stuff(you don't want to drink that), there's the pot that's cold and a dried up sludge of stuff(you could probably eat that), there's the pot that's just plain water with some grass(won't make much difference if you do), there's the pot with lukewarm fluids and a nice assortment of food. The principle being, that no matter the size, the stage, the placement of the pot, you'll have to go through all of these stages before you can eat, clean the pot and get some new stuff to put it in.
So I think that whether or not a country is a melting pot or not is irrelevant.
What is relevant is
is the pot being cleaned, is there always more stuff to put in it, how high tech is the pot and do
we even have a fire going?
But most importantly Who's eating from the pot?
