Which of president clinton’s efforts to change domestic policy failed?

The correct answer is A) The Union's effectiveness at the Battle of Antietam.

The Emancipation Proclamation was supposed to free slaves in the rebellious states (aka the Confederate States of America). Even though this document did not free the slaves in the rebellious states, as every Confederate state ignored this law, it did make it so that African Americans who escaped from the South could join the Union army in the North. This was a significant turning point of the war, as it shows that Lincoln's purpose in fighting this war is to end the institution of slavery within the United States.