[alexeisadeski3]

Immigration wasn't restricted until the 20th century (in any meaningful way), and the US didn't seem to suffer too bad.

[MichaelGG]

I'd wager that A: the disparity between countries is larger and more well-known now, and B: the ease of physically travelling to the US is far easier now.

[alexeisadeski3]

And I'd wager that the cost of living is higher now, relative to the other countries.

[wpietri]

The Model T started production in 1908 and the first commerical airline flight was in 1914. The state of the art for sea transportation around then was the Titantic, which sank in 1912. So maybe that had something to do with it.