Yes not only the Americans but the allied forces did agree to help rebuild Hiroshima and Nagasaki after the second world war. The head of Supreme Command of Allied Powers (General Douglas MacArthur) was head of arranging the rebuilding of these two cities and to look after the defence of Japan while building was invested by the Japanese government. It took around 15 years to rebuild Japan.

Great Britain, the Soviet Union, and the Republic of China had a massive role as part of an “Allied Council,” MacArthur had the final authority to make all decisions. The occupation of Japan can be divided into three phases: the initial effort to punish and reform Japan, the work to revive the Japanese economy, and the conclusion of a formal peace treaty and alliance.