In terms of GPD the US was the world's largest economy well before World War I. Europe choosing to self-immolate twice before mid-century only served to widen the gap.
But we are talking about US getting brains from all over Europe. The combined GDP of the top 3 European countries (Germany, UK, France) pre WW1/2 is larger than the US, just as the GDP per capita of any individual European country pre WW1/2 is higher as well.
Is that true? https://substackcdn.com/image/fetch/f_auto,q_auto:good,fl_pr...
They go the other way.
The US surpassed the UK in per capita income in the 1880s. However, American yeomen farmers, factory workers etc. were far better off than (non-UK) Europeans even in 1800, hence millions of Europeans immigrating. By 1913, the American was still earning almost twice as much as the German or French: https://en.wikipedia.org/wiki/List_of_regions_by_past_GDP_(P...