The federal government did not have enough power causing the states to be chaotic due to how much power they had under the Articles of Confederation.
I'm sorry I don't understand it
The most notable is the atomic bomb. Roosevelt became aware that the Nazis were trying to develop one, so he started the "Manhattan Project" which was a group of elite scientists tasked with developing their own atomic bomb. They eventually succeeded, and in 1945, we dropped the bomb on Japan.
