No English King was executed after the English Civil War. The execution of King Charles I occurred during the Civil War.

No - the English had nothing to do with the American Civil War.

After World War I, political radicalism saw the rise of communist movements influenced by the Russian Revolution, such as the establishment of the Soviet Union and the spread of socialist ideas across Europe. Social radicalism also emerged as a response to the failures of the pre-war political systems, with movements advocating for greater equality, women's rights, and civil liberties.

Third English Civil War happened in 1649.

Wars are usually named after the winner of that war. Due to the fact that the war is called the English Civil War the English won the war.