Was the US the only country involved with the Manhattan Project?

The United States is known for the Manhattan Project and the dropping of nuclear bombs on Japan. However, there were other countries involved. During World War II, the allied powers included the four main countries of United Kingdom, China, U.S. and the Soviet Union. Both the Soviet Union and the United States didn’t enter the war until 1941. There were other countries that were part of the allied powers including India, Canada, Australia, New Zealand, South Africa, Nepal, Ethiopia, Brazil, Philippines, Mongolia, Mexico and Cuba.

The Axis powers included Italy, Romania, Japan, Germany, Bulgaria, and Finland. With the Manhattan Project, the United Kingdom and Canada also helped with the making of these bombs. Actually, Canada had a few project sites in their country.