The United States of America has received more immigrants since its foundation than all the other countries of the world put together. From 1836 to 1914, more than 30 million Europeans migrated to the US.
The trend was bucked in the 1930s owing to the Great Depression, which hit the US hard and lasted more than ten years there. In the early part of the decade, more people emigrated from the United States than immigrated to it.
But even in the 1930s, the excellence of America's academic institutions has always been a big draw for European intellectuals. As far as management thinkers are concerned, these include Drucker, Hopf, Juran, Levitt, Munsterberg, Schumpeter and Wertheimer.