My impression of Scandinavian startups (though I could be wrong) is that those who move to the U.S. really are mostly concerned about the business side of thing

My impression of Scandinavian startups (though I could be wrong) is that those who move to the U.S. really are mostly concerned about the business side of things (investment, customers, vendor/partner relationships, and at strategic times, capital-gains taxes). You can see that in the fact that they often do a half-move, where they move everything except the technical part of the company. Unity3d is one prominent example: the headquarters officially moved from Copenhagen to San Francisco, and any kind of announcement that makes headlines comes out of the SF office, but the core engine devs are all still in Copenhagen. If it were about the technical culture, you'd expect them to want to move the actual technology work to Silicon Valley too, but it was mainly the business side.