Well here's the thing.
America has the better capacity to pay and employ experts. This, combined with excellent technical and engineering universities just naturally makes America the hub of a lot of talented people.
Europe's got good schools too, though their pay capability isn't as high... and I know of many Europeans who want to go and work in America, but not seen many Americans wanting to go work in Europe.
Also I know of many Koreans going over to make more money in the US... in general, a lot of the world suffers from brain drain because of America's pay power. This is what gives America the edge.