The US was isolationist during much of world war 2 and had a “cash and carry” approach towards selling arms to US allies during initial part of the war which after much deliberation became a lend-lease arrangement that had been against the desires of the American people who did not want to get dragged into conflict that had its center stage in Europe. These financial arrangements made the US incredibly wealthy, essentially extracting centuries of colonial and slavery based loot from the Brits, which allowed it to become the global hegimon it is today (for now).