I simply don’t think that anybody else was likely to get beyond the “eggheads and experiments” stage. The resources required were stupendous and with a war on… Well the needs of “right now” have a way of focusing one’s attention and efforts. It took the Soviets ~4 years working on a crash project, without a war to distract them, with the aid of some spies to cut down on dead ends and knowing with absolute certainty that it was possible. I’m mostly curious as to what the US would have done with all the men and money that it spend on Oak Ridge and Hanford if they hadn’t been working on the bomb. Probably more ships, aircraft, tanks, and trucks. And how would that have affected the outcome of the war? It could conceivably have ended earlier.
Edited to add some numbers from Wikipedia
The project expenditure through 1 October 1945 was $1.845 billion, equivalent to less than nine days of wartime spending, and was $2.191 billion when the AEC assumed control on 1 January 1947. Total allocation was $2.4 billion. Over 90% of the cost was for building plants and producing the fissionable materials, and less than 10% for development and production of the weapons.[320][321]
A total of four weapons (the Trinity gadget, Little Boy, Fat Man, and an unused bomb) were produced by the end of 1945, making the average cost per bomb around $500 million in 1945 dollars. By comparison, the project’s total cost by the end of 1945 was about 90% of the total spent on the production of US small arms (not including ammunition) and 34% of the total spent on US tanks during the same period.[319] Overall, it was the second most expensive weapons project undertaken by the United States in World War II, behind only the design and production of the Boeing B-29 Superfortress.[322]
