It's hardly the only measure, but Americans had won
If the World Wars never happen which started the outflow of European capital and brains to the US, what would that do to the US university system? The US really only managed to catch up to and exceed the Europeans after WW2 when the best minds in Europe fled the Nazis and aftermath of the war, upgrading both the British and US universities by their addition to the faculty. However if the Germans and all other stayed at home and continued to make their universities the hubs of science and other fields would the US system ever be world class or would the Europeans just keep their lead?
It's hardly the only measure, but Americans (as in US citizens) had won 13 Nobels in the sciences by 1939, ranging from AA Michelson in 1907 to Ernest Lawrence in 1939 (both Physics); the others included Richards (Chemistry), Millikan (P), Compton (P), Langmuir (C), Morgan (Physiology/Medicine), Whipple (PM), Murphy (PM), Minot (PM), Urey (C), Anderson (P), and Davisson (P).
There were 35 Germans in the same period, but several of those winners were born outside of Germany, and ended up there for various practical reasons - Kuhn and Lenard were both born in Austria, for example, and Ostwald in Russia.
Britain had 22 (including several born overseas), France had 17 (Marie Curie won twice), and so on.
It's also worth mentioning that "Big Science" and US federal support for research universities was hardly unknown in the Nineteenth Century; the National Academy of Sciences was founded in 1863, and the Morrill acts of 1862 and 1890 led to federal support for such minor institutions as Rutgers (founded 1766), MIT (1861), and Cornell (1865), as well as campuses of the universities of California, Illinois, and Wisconsin, Purdue, Iowa State, Kansas State, Michigan State, Ohio State, Penn State, Texas A&M, Virginia Tech, and many others.
There is also the reality that minor universities such as Princeton, Harvard, Yale, etc, as well as Caltech (founded as such 1910), Rennsalear, etc. all predated WW I, by (in the case of the Ivies) centuries...
Along with the Nobel, there's also the Copley, awarded by the Royal Society, which was first awarded to an American, the mathematician Josiah Willard Gibbs, (Yale, PHd, 1863) in 1901; Gibbs had won the Rumford from the American Academy of Arts and Sciences (founded in 1780!) in 1880... along with such minor lights as Michelson, Edison, Hale, AH and KT Compton, Shapley, and a few others.
My point being, that given the realities of the world economy by (say) 19143 (Bairoch via Kennedy) the following rankings in terms of total industrial potential (UK in 1900 being 100):
US - 298.1
GE - 137.7
GB - 127.2
RE - 76.6
FE - 57.3
AH - 40.7
JE - 25.1
IE - 22.5
It is worth noting the US had surpassed the UK in the same measure in 1900, 127.8 vis a vis 100...
My point being, it will take more than the absence of the world wars to reverse the US climb to superpower state, economically, militarily,
and technologically.
Best,