America needed huge funding, many top experts, some secret science, and good luck and still did not have a Bomb in time to affect the war in Europe.
America only developed the A-bomb because the British bomb project, codenamed "
Tube Alloys"was considered too valuable to keep in range of Luftwaffe bombing, so it was moved to the USA.
Under the terms of the Quebec Agreement, the technology resulting from the project, now called the Manhattan Project, was to be shared between Britain and the US; However Truman reneged on the deal when he saw how powerful the resulting weapon actually was, and decided not to share with anyone (except the Soviet Union, who had shared the details on their own initiative and without asking for permission).
The British responded by building their own A-bomb,
with blackjack and hookers and then their own H-bomb, after which the Americans relented and resumed information sharing.
Hitler never got anywhere close to developing atomic weapons, partly because he derided atomic physics as "Jewish science", and partly because the physicists he did have, particularly Heisenberg, deliberately downplayed the prospects of ever developing a workable bomb.
Of course, nobody in the Allied camp knew this, and they were very reasonably terrified that he might get there first.
