In and after World War 2 and for time afterwards the term good Germans was used in English-speaking countries for Germans who were opposed to the Nazi regime.
Yankee refered to the Union (Northen) Troops and people. It was meant as a slur and a bad term, and was used by the Confederates.
The term used by southerners for a return to Democratic white rule was redeemers.
During World War 2, a "Yank" referred to an American soldier. The term was often used by civilians and other military personnel from different countries to refer to American servicemen. The term "Yank" was derived from "Yankee," a term used to describe people from the United States.
If you mean used it in an act of warfare, as opposed to a test, the only country to do so has been the USA (Hiroshima and Nagasaki, 1945)
Slang
vinyl
The arguments used to justify and oppose secession
To dismount, I believe. As opposed to mount (to get on a horse).
A "brooch" is the term for a decorative pin or jeweled pin, as opposed to a safety pin.
The term used for milk products is "dairy" (as opposed to diary, which is a personal journal).
PC stands for Personal Computer. This was a term which was used to signify that the computer was for the personal use of one person as opposed to a mainframe computer which would be used by several people at the same time operating from remote 'terminals'.
Abraham Lincoln opposed secession but initially did not believe that the Union should be held together by force. He preferred a peaceful resolution but ultimately resorted to force to preserve the Union during the Civil War.
The term of "Allies" was the most often used term to describe the coalition of countries opposed to the Axis powers. Another similar term was "allied forces". Each term means the same thing.
The term "yacht" is used to designate a pleasure boat as opposed to a working boat. It can be used in reference to a power boat or a sail boat.
A "day boat" is a term usually used for a fishing charter that goes out for the day, as opposed to hourly or overnight. There may be other definitions.
The people of West Virginia were unhappy when Virginia voted for secession from the Union. About a month later, the people of West Virginia had the Wheeling Convention to become a separate state. Tennessee voted to not send delegates to a secession convention.