Overtook UK in Per-capita GDP by 1913
It was already the world's pre-eminent economic power on the eve of WWII
Even without WWII, US would've been the preeminent economic powerhouse of mid 20th century
Now decolonization was always in the offing, even if there had been no World war 2
The colonies (esp India) were becoming too hot to handle
Let's not underrate Gandhi
It is not yet the largest economy in the world even in aggregate terms, despite being 3 times as populous as US
It will likely not even approach 50% of US Per-capita income in market exchange rates for another 20-25 years
But it's position is nowhere close to the enormous power and influence of US circa 1950