If you're asking, who else could have duplicated the Manhattan Project? ... I'm honestly not sure if anybody else could have. The Manhattan Project was a ridiculous use of resources that was only possible because the US was basically safe from domestic enemy attacks. The amount of money wasn't unique to it — Germany spent more on the V-1 and V-2 projects, for example — but the amount of people was ridiculously huge (around 600,000), and the size of the facilities needed were incredible (and would have been easy/obvious bombing targets anywhere else), and the scientific manpower at the US's disposal was ridiculous even by modern standards (both the domestic powerhouses and all of the foreign ones who emigrated over)... it's a rather singular thing. No other country since has made an atomic bomb in as little time as the US did during the war, which is a sign of something.
But what if we imagined a slower, cheaper, more focused program? Here's a list of the main contenders with comments:
the UK — could maybe have done it smaller, slower, and on the cheap, but being within bombing range of Germany would have made it hard to pull off
France — potentially capable of doing it one way or another except for the whole "invaded by Germany" thing
the USSR — if they hadn't been struggling to keep the Germans at bay, they probably could have pulled it off, though not as fast as the Americans because their uranium sources were much more limited during the war
Germany — might have had a chance if they hadn't suffered so much brain drain from their anti-Semitic policies, and if they had control of the skies (e.g. safe from bombing)
Japan — if they had focused on it, drafted a lot of Chinese/Korean labor into it, and not been so vulnerable to bombing from both West and East, then possibly
Then again, this all gets into really speculative "what if?" territory. But you can see that the cards were really stacked, in the end, for the US to be the one to make it, even though it was an incredibly difficult thing for them to pull off.