> It reached the US, ...

Behind that phrase is a whole story in itself, covered in the book "Wizards of Oz How Oliphant and Florey helped win the war and shape the modern world" by Brett Mason.

Mark Oliphant was heading a lab and tasked Otto Frisch and Rodolf Perierls with figuring out whether an atomic bomb was possible, as they were not cleared to work on radar. They concluded it was possible and wrote a two part memorandum: 'On the Construction of a "Super bomb"; based on a Nuclear Chain Reaction in Uranium' and 'Memorandum on the Properties of a Radioactive "Super-bomb"' [1,2]

Oliphant sent this report up the chain and it lead to the formation of the MAUD committee in the UK. The UK didn't have the resources to build an atomic bomb, so what was known was sent to the US. Oliphant hopped on a plane and did a tour of the US, doing technology transfer, mainly for radar, but also for an atomic bomb. Most people in the US ignored the MAUD report and Oliphant could not get traction on the atomic side. In desperation Oliphant breached security and briefed Ernest Lawrence who at the time was not cleared, also providing him with a summary of the MAUD report. Robert Oppenheimer joined the discussion between Oliphant and Lawrence. Lawrence phoned Arthur Compton in Chicago. From there the USA listened.

[1] https://web.stanford.edu/class/history5n/FPmemo.pdf

[2] https://en.wikipedia.org/wiki/Frisch%E2%80%93Peierls_memoran...