The correct answer to this open question is the following.
Based on the Judicial Branch the court case that stands out to me the most is Brown v. the Board of Education of Topeka, Kansas.
For me, this is one of the most important cases in the history of the United States.
The case was decided on May 17, 1954. The Supreme Court decided that state laws in the US public school system that kept racial segregation were unconstitutional.
This was a major advancement in the country regarding the shameful subject of racism. After the US Supreme Court decision, racial segregation in public schools of America ended, at least in theory and by judicial mandate.
Answer:
After England won the wars, new taxes were made to pay for the debt from the wars.
The word or phrase to fill into the gap is the "Ku Klux Klan", an extreme right organization calling for what they would call a "purification" of the US-American society.