As has been pointed out by others, Swedes in America are pretty darn prosperous. I would not be surprised if they are on average better off than those who stayed in the Old Country.
- Neither would I. Swedes and Scandinavians in general are, evidently, good at doing business.
Especially during the early phase of mass-emmigration from Sweden around the mid 19th century, there was little opportunity for gifted businessmen back in the old country. Sweden's economy might have exploded with growth from around 1870, but since America remained a far richer country at least until the outbreak of WWII, people continued to emigrate to USA from Sweden.